Maintaining functional working memory through job activities: A study among patients with schizophrenia enrolled in a supported employment program

Abstract

BACKGROUND:

Employment is crucial in rehabilitation of patients with schizophrenia. It may have positive effects on cognitive function, including working memory.

OBJECTIVE:

The objective of this study was to look for evidence to confirm continuous job activities could maintain functional working memory in patients with schizophrenia.

METHODS:

This was a cross-sectional study involving patients with schizophrenia enrolled in supported employment (SE) program. Informed consent was obtained. Socio-demographic, employment, and clinical data were acquired from interview and clinical notes. Mini International Neuropsychiatric Inventory (M.I.N.I) was used to confirm the diagnosis of schizophrenia. Working memory was evaluated using Weschler Memory Scale Third Edition -Letter-Number Span and Spatial Span.

RESULTS:

118 patients were recruited with a mean age of 43.76 years old (SD = 8.96). Most were male, Malays, Muslims, single, and received at least secondary education. There was a significant association between working memory and employment outcome (χ² = 20.835, p < .001), and past work history (χ² = 10.077, p = 0.002). Multiple logistic regression indicated that the employment outcome (adjusted OR: 12.50; 95% CI: 2.55–61.21; p = 0.002) and past work history (adjusted OR: 3.36; 95% CI: 1.05–10.70; p = 0.041) were significant predictors of working memory among patients with schizophrenia in SE program.

CONCLUSION:

This study indicated that continuous job activities could maintain functional working memory in patients with schizophrenia.

Keywords

Schizophrenia supported employment working memory cognitive function psychosocial rehabilitation

1 Introduction

Schizophrenia is a serious and chronic mental disorder. It leads to disturbance of a person’s thought, perception, emotion, behaviour, and cognitive function. Based on the American Psychiatric Association’s (2013) Diagnostic and Statistical Manual of Mental Health Disorders (5th ed.; DSM-5), the diagnosis of schizophrenia is established when a person presented with at least 2 (or more) of either delusions, hallucinations, disorganized speech, grossly disorganized or catatonic behaviour, and negative symptom. A person with schizophrenia will also have deterioration of function in important aspects of their life such as work, relationship, and self-care.

Among the first symptoms observed in individuals who were diagnosed with schizophrenia is cognitive deficit (Tripathi et al., 2018). About 61–78% of patients with schizophrenia experienced significant level of cognitive deficit (Green, 2006). Patients with schizophrenia performed significantly worse compared to healthy controls in scholastic measures such as vocabulary, reading, language, sources of information, math, and composite by the time psychosis emerged in late adolescence or early adulthood (Keefe & Fenton, 2007). These deficits manifest during the period where full occupational and social functioning is anticipated from an individual. More than half (68%) of patients with schizophrenia in Malaysia are unemployed based on the National Schizophrenia Registry 2008 (Aziz et al., 2008).

Working memory, executive function, and processing speed were among the most duplicated impairments (Reichenberg, 2010). The central cognitive deficit in schizophrenia is the impairment in working memory. Working memory is the capacity to actively store various pieces of perceived information and use this information over a short period which is essential for learning, reasoning, and understanding (Baddeley, 1992). These impairments in working memory, particularly encoding and maintenance of visual-spatial, and auditory tasks performance have been found in patients with schizophrenia compared to healthy controls (Forbes et al., 2009). Employment has been given highlights in recent psychosocial intervention of patients with schizophrenia. Employment promotes independence, sense of accomplishment, improves cognitive performance, self-esteem, and social functioning (Charzyńska et al., 2015). Supported employment (SE) refers to “competitive work in an integrated setting with ongoing supports for individuals with the most severe disabilities or transitional employment for individuals with the most severe disabilities due to mental illness” (Federal Register, 2001). A Cochrane systematic review found that SE increased the chances of obtaining any employment and the duration in competitive employment when compared to other vocational models for those with severe mental illness (Kinoshita et al., 2013).

Individual Placement and Support (IPS) is an evidence-based model of supported employment for individuals with severe mental illness which focuses on assisting patients in attaining and succeeding in competitive employment (Bond et al., 2008; Marshall et al., 2014). Those in the IPS program were found to have better vocational outcomes in terms of shorter time for job placement, increased chances of obtaining as well as maintaining competitive employment. They also have longer employment length and tenure with higher total pay (Frederick & VanderWeele, 2019).

In a study which compared 117 people with schizophrenia with 77 healthy participants, patients with schizophrenia who were employed performed better on the MATRICS Consensus Cognitive Battery (MCCB), especially in working memory and processing speed in comparison with unemployed patients (August et al., 2012). Besides that, significant improvement in working memory and executive function has been observed with work therapy (Bell et al., 2001). In a study conducted locally, an essential factor in obtaining and maintaining employment in patients with schizophrenia is a good cognitive function, particularly in working memory, attention, and executive function (Midin et al., 2011). The relationship between employment and cognitive function could be bidirectional; better cognitive function could lead to better work performance or on the other hand, employment could improve cognition (Lystad et al., 2014).

While there are studies that looked at socio-demographic and clinical factors that are associated with working memory, executive function, and processing speed in patients with schizophrenia (Harvey et al., 2001; McGurk & Meltzer, 2000; Normala et al., 2009), it is also essential to study the association between employment factors with these cognitive domains. Besides, most of the studies demonstrated the effect of cognitive function on employment, and there is still a lack of evidence to confirm employment as a predictor of better cognitive performance. Working memory impairment is thought to be a central cognitive deficit in schizophrenia (Forbes et al., 2009). Working memory was also significantly influenced by the history of previous employment (Lystad et al., 2014), and improvement in employment outcome (Nuechterlein et al., 2011). Hence this study was conducted to look for evidence to confirm continuous job activities could maintain functional working memory in patients with schizophrenia.

2 Methods

2.1 Study design and setting

This was a cross-sectional study conducted in the Occupational Therapy Unit of Hospital Permai, Johore which is a mental health institution in Malaysia. Participants of the study were patients with schizophrenia enrolled into the supported employment program under the unit. Supported employment (SE) is one of the interventions listed under the Rehabilitation and Recovery Orientated Services in the Malaysia Psychiatric and Mental Health Services Operational Policy (Medical Development Division Ministry of Health Malaysia, 2011). The SE program practices the “place and train” method. Occupational therapists functioned as the case managers, supervised by a medical officer and psychiatrist to coach the patients. Only those who showed interest in employment were enrolled in the program. The type of employment chosen for a patient was based on the patient’s preference and availability of the jobs after discussion with the job coach. Each patient was assigned with a job coach according to the area where the patient was working. The job coach helped the patients to find and secure a job. They also assisted the patients with any issues related to the employment, including logistic and placement matters.

2.2 Selection criteria

Participants were selected using simple random sampling. At the time of the study, there were 160 patients enrolled in the SE program. The list of patients that fulfilled the inclusion criteria were obtained, and their names were coded with a number each. The number was written in a piece of folded paper, and put into a bowl. Then, the folded papers were selected until the sample size was achieved. Using OpenEpi, the sample size required was 98 patients, and the possible attrition rate was 20% (20 patients); hence, a total of 120 patients were recruited in this study. The study included patients who were enrolled in the SE program for at least 3 months, diagnosed with schizophrenia, clinically stable and not acutely psychotic, aged between 18 and 60 years old, and able to read, write, and understand Malay or English. We excluded patients with significant medical and neurological disorder, cognitive impairment (e.g., neurocognitive disorder, epilepsy, head injury, and cerebrovascular disease), and those with intellectual disability.

2.3 Study instruments

2.3.1 Socio-demographic questionnaire

The socio-demographic questionnaire was developed based on literature review. It consisted of 3 parts, which assessed participant’s socio-demographic factors (age, gender, race, religion, education, and marital status), employment factors (employment outcome, types of employment, duration of enrolment, job tenure, salary, getting the preferred job, types of job, and past work history), and clinical factors (duration of illness, the onset of illness, types of medication, number of relapses, and medication adherence). The type of employment was classified into competitive job (job in the ‘community setting’ where the patient has the same responsibility and given the same salary similar with other non-disabled employees), ‘social enterprise’ where patient run enterprises with minimal assistance from the support staff, and ‘smart partnership’ where employers provided the job for the hospital.

2.3.2 Mini International Neuropsychiatric Inventory (M.I.N.I) 7.0.2

The M.I.N.I 7.0.2 was designed as a brief structured Mini International Neuropsychiatric Inventory interview for the major psychiatric disorders in DSM-5 and ICD-10. It is an interviewer rated instrument. The diagnosis of schizophrenia was confirmed using M.I.N.I 7.0.2, Module K (Sheehan et al., 1998).

2.3.3 MATRICS Consensus Cognitive Battery (MCCB)

The MATRICS Consensus Cognitive Battery (MCCB) was initially designed to develop a consensus battery for clinical trial of cognition-enhancing treatments for schizophrenia to evaluate pharmacological agents that target cognitive deficits in schizophrenia for FDA approval. Furthermore, it also aims to implement a standardized assessment of cognition in schizophrenia (Nuechterlein et al., 2008). The MCCB includes ten tests from seven different domains that were chosen to represent cognition in schizophrenia. The domains are speed of processing, working memory, verbal learning, visual learning, reasoning and problem solving, social cognition, and attention or vigilance.

In this study, working memory was assessed using the Wechsler Memory Scale-Third Edition (WMS-III): Spatial Span and Letter Number Span tests. The raw score from each test was entered into the MCCB Scoring Programme and T score was generated by the programme. The normal value for the T score for working memory is 50±10 (Kern et al., 2008). Therefore, those who scored below the normal range was considered to have cognitive deficit. It was dichotomously defined as no impairment if the score was 40 or above and impaired if the score was below.

2.4 Data collection

The case notes were reviewed to determine all patients with schizophrenia in the supported employment program of the hospital that fulfilled inclusion criteria to be recruited into the study. Simple random sampling was then used to select the patients. An explanation and patient information sheet about the study was given to all patients. Written informed consent was obtained during the scheduled appointment. The patient was interviewed by the investigator to get the socio-demographic, employment, and clinical data. Diagnosis of schizophrenia was determined by the treating psychiatrist before referral for enrolment into the SE program and confirmed with the Mini International Neuropsychiatric Inventory (M.I.N.I). Working memory was assessed using the Wechsler Memory Scale-Third Edition (WMS-III): Spatial Span and Letter Number Span tests. The results from each test were entered into the MATRICS Consensus Cognitive Battery (MCCB) Scoring Program, and the program generated the T score for the domain. It was dichotomously defined as no impairment if the score was 40 or above and impaired if the score was below 40.

2.5 Data analysis

The data was analysed using International Business Machines (IBM®) Statistical Package for Social Science (SPSS) version 24.0. The level of working memory, socio-demographic, employment factors and other clinical variables were described in the results. The continuous variables were reported in mean and standard deviation. On the other hand, categorical variables were reported in frequency and percentage. The data obtained from the MATRICS Consensus Cognitive Battery (MCCB) were organised and analysed. Chi-square test, independent t-test and multiple logistic regression tests were used to determine the association between socio-demographic, employment, and clinical factors with working memory. After chi-square and independent t-test, the results were further analysed using multiple logistic regression. Multivariate analysis was done to find the independent variables that best predict the outcome variable. Independent variables that had significant value (p < 0.05) during chi-square and independent t-test analysis and clinically significant were subjected to multiple logistic regression.

2.6 Ethical consideration

The research was approved by the Research Ethics Committee, Universiti Teknologi MARA (UiTM), Malaysia (Reference Number: 600-IRMI (5/1/6)) and the National Medical Research and Ethics Committee (MREC) of the Ministry of Health, Malaysia via the National Medical Research Registry (NMRR) (Registration number: NMRR-17-3366-38938).

All procedures performed in this study involving the participants were done in accordance with the ethical standards of the Committee on Human Experimentation of the institution in which the experiments were done or in accord with the Declaration of Helsinki of 1975.

3 Results

3.1 Socio-demographic characteristics

A total of 120 potential participants met eligibility criteria. However, two of them refused to join the study, and the remaining 118 participants who provided consent were enrolled. The participants’ age (mean±SD) was 43.76±8.96 and ranged between 36–45 years old. The majority were male (93; 78.8%), Malays (81; 68.6%), Muslims (84; 71.2%), single (83; 70.3%), and received at least secondary education (82; 69.5%). Refer to Table 1 for further details of the socio-demographic characteristics of the participants.

Table 1
Socio-demographic characteristics of patients

Variables M±SD Number Percentage

(n) (%)

Age (in years) 43.76±8.957

Age group

18–25 1 0.8

26–35 22 18.6

36–45 53 44.9

46–60 42 35.6

Gender

Male 93 78.8

Female 25 21.2

Ethnicity

Malay 81 68.6

Chinese 24 20.3

Indian 9 7.6

Others 4 3.4

Religion

Islam 84 71.2

Buddhist 19 16.1

Hindu 8 6.8

Christian 4 3.4

Others 3 2.5

Marital status

Single 83 70.3

Married 16 13.6

Divorce/Separated/Widowed 19 16.1

Education level

No formal education 6 5.1

Primary 17 14.4

Secondary 82 69.5

Tertiary 13 11.0

Variables	M±SD	Number	Percentage
Age (in years)	43.76±8.957
Age group
18–25		1	0.8
26–35		22	18.6
36–45		53	44.9
46–60		42	35.6
Gender
Male		93	78.8
Female		25	21.2
Ethnicity
Malay		81	68.6
Chinese		24	20.3
Indian		9	7.6
Others		4	3.4
Religion
Islam		84	71.2
Buddhist		19	16.1
Hindu		8	6.8
Christian		4	3.4
Others		3	2.5
Marital status
Single		83	70.3
Married		16	13.6
Divorce/Separated/Widowed		19	16.1
Education level
No formal education		6	5.1
Primary		17	14.4
Secondary		82	69.5
Tertiary		13	11.0

SD = standard deviation.

3.2 Employment characteristics

The (mean±SD) duration of enrolment in the program was 30.81±25.94 months, while the duration of job tenure was 23.08±29.39 months. Of the total 118 participants, 102 (86.4%) had successful employment. The most common type of employment chosen by the participants was ‘competitive’ (80; 67.8%), followed by social enterprise (22; 18.6%), and smart partnership (16; 13.6%) respectively. The (mean±SD) salary was RM818.68±347.69 per month. A total of 84 (71.2%) participants received a salary of RM 1000 or less per month, while 34 (28.8%) participants received income of more than RM 1000. Majority of the participants obtained job according to their preferences (98; 83.1%) and had a past work history of 1 month or more (82.2%). For the type of jobs, most of them worked in service jobs (46.6%) and manual labour (39.8%). Table 2 summarises the employment characteristics of the patients.

Table 2
Employment characteristics of patients

Variables M±SD n (%)

Duration of enrolment (months) 30.81±25.94

Job tenure (months) 23.08±29.39

Employment outcome

Successful 102 (86.4)

Unsuccessful 16 (13.6)

Types of employment

Competitive 80 (67.8)

Smart partnership 16 (13.6)

Social enterprise 22 (18.6)

Salary (RM) 818.68±347.69

≤1000 84 (71.2)

> 1000 34 (28.8)

Getting preferred job

Yes 98 (83.1)

No 20 (16.9)

Types of job

Professional and administration 2 (1.7)

Clerical 4 (3.4)

Sales 10 (8.5)

Service 55 (46.6)

Manual labour 47 (39.8)

Past work history

< 1 month 21(17.8)

≥1 month 97 (82.2)

Variables	M±SD	n (%)
Duration of enrolment (months)	30.81±25.94
Job tenure (months)	23.08±29.39
Employment outcome
Successful		102 (86.4)
Unsuccessful		16 (13.6)
Types of employment
Competitive		80 (67.8)
Smart partnership		16 (13.6)
Social enterprise		22 (18.6)
Salary (RM)	818.68±347.69
≤1000		84 (71.2)
> 1000		34 (28.8)
Getting preferred job
Yes		98 (83.1)
No		20 (16.9)
Types of job
Professional and administration		2 (1.7)
Clerical		4 (3.4)
Sales		10 (8.5)
Service		55 (46.6)
Manual labour		47 (39.8)
Past work history
< 1 month		21(17.8)
≥1 month		97 (82.2)

SD = standard deviation.

3.3 Clinical characteristics

A majority had chronic illness; more than two-third had had schizophrenia for more than 10 years. Majority of the patients had onset of illness between the age of 15 to 30 years old (94; 79.7%).

In terms of medication, more than half of the patients were treated with atypical antipsychotics (72; 61%), while 37 (31.4%) participants were treated with typical antipsychotics, and only 9 (7.6%) of them had a combination of both antipsychotics. Most of them had good adherence to medication (108; 91.5%). Also, 74 (62.7%) of the patients had more than 5 episodes of relapses throughout the illness. Refer to Table 3 for further details of the clinical characteristics.

Table 3
Clinical characteristics of patients

Variables Number (n) Percentage (%)

Duration of illness

0–5 years 10 8.5

6–10 years 18 15.3

11–20 years 54 45.8

> 20 years 36 30.5

Age of onset (years)

15–30 94 79.7

31–39 17 14.4

≥40 7 5.9

Types of medication

Typical 37 31.4

Atypical 72 61.0

Combination 9 7.6

Number of relapses

0–5 times 44 37.3

> 5 times 74 62.7

Adherence to medication

Yes 108 91.5

No 10 8.5

Variables	Number (n)	Percentage (%)
Duration of illness
0–5 years	10	8.5
6–10 years	18	15.3
11–20 years	54	45.8
> 20 years	36	30.5
Age of onset (years)
15–30	94	79.7
31–39	17	14.4
≥40	7	5.9
Types of medication
Typical	37	31.4
Atypical	72	61.0
Combination	9	7.6
Number of relapses
0–5 times	44	37.3
> 5 times	74	62.7
Adherence to medication
Yes	108	91.5
No	10	8.5

3.4 Status of working memory and its contributing factors

Table 4 showed the status of working memory and its contributing factors. Of the total, 43 (36.4%) participants had impairment of working memory. There was a statistically significant association between working memory and marital status (χ² = 4.580, p = 0.032) with a higher percentage of normal working memory among patients who were married (87.5%) compared to being single, divorced, separated, or widow (59.8%). There was a significant association between working memory and employment outcome (χ² = 20.835, p < 0.001) and past work history (χ² = 10.077, p = 0.002). Patients who had successful employment and worked more than a month in the past were found to have a higher percentage of no impairment in working memory; 71.6% and 70.1% respectively. Other socio-demographic, employment, and clinical factors were not associated with the status of working memory.

Table 4
Working memory and possible contributing factors

Impairment of working memory

Variables Yes n (%) No n (%) χ ² p

Socio-demographic factors

Age (years) ≤45 24 (31.6) 52(68.4) 2.179 0.140

> 45 19 (45.2) 23 (54.8)

Gender Male 31 (33.3) 62 (66.7) 1.830 0.176

Female 12 (48.0) 13 (52.0)

Ethnicity Malay 29 (35.8) 52 (64.2) 0.045 0.831

Non-Malay 14 (37.8) 23 (62.2)

Religion Muslim 29 (34.5) 55 (65.5) 0.462 0.496

Non-Muslim 14 (41.2) 20 (58.8)

Marital status Married 2 (12.5) 14 (87.5) 4.580 0.032 ^*

Unmarried 41 (40.2) 61 (59.8)

Education level ≤Secondary 39 (37.1) 66 (62.9) 0.203 0.652

> Secondary 4 (30.8) 9 (69.2)

Clinical factors

Duration of illness ≤10 years 13 (46.4) 15 (53.6) 1.581 0.209

> 10 years 30 (33.3) 60 (66.7)

Age of onset (years) ≤30 years 31 (33) 63 (67) 2.392 0.122

> 30 years 12 (50) 12 (50)

Types of medications Atypical 25 (35.7) 45 (64.3)

Typical 14 (37.8) 23 (62.2)

Combination 4 (36.4) 7 (63.6) 0.047 0.977

Number of relapses ≤5 14 (31.8) 30 (68.2) 0.647 0.421

> 5 29 (39.2) 45 (60.8)

Employment factors

Employment outcome Successful 29 (28.4) 73 (71.6) 20.835 < 0.001 ^*

Unsuccessful 14 (87.5) 2 (12.5)

Types of employment Competitive 27 (33.8) 53 (63.3) 2.183 0.336

Smart partnership 5 (31.3) 11 (68.8)

Social enterprise 11 (50.0) 11 (50.0)

Salary ≤1000 31 (36.9) 53 (63.1) 0.027 0.869

> 1000 12 (35.3) 22 (64.7)

Getting preferred job Yes 39 (39.8) 59 (60.2) 2.810 0.094

No 4 (20.0) 16 (80.0)

Types of job Manual labour 19 (40.4) 28 (59.6) 1.418 0.492

Services 17 (30.9) 38 (69.1)

Others 7 (43.8) 9 (56.3)

Past work history < 1 month 14 (66.7) 7 (33.3) 10.077 0.002 ^*

≥1 month 29 (29.9) 68 (70.1)

t P

Duration of enrolment (months) 29.72 (16.18) 31.44 (30.23) –0.345 0.731

Job tenure (months) 19.58 (21.58) 25.09 (33.02) –0.980 0.329

	Impairment of working memory
Socio-demographic factors
Age (years)	≤45	24 (31.6)	52(68.4)	2.179	0.140
	> 45	19 (45.2)	23 (54.8)
Gender	Male	31 (33.3)	62 (66.7)	1.830	0.176
	Female	12 (48.0)	13 (52.0)
Ethnicity	Malay	29 (35.8)	52 (64.2)	0.045	0.831
	Non-Malay	14 (37.8)	23 (62.2)
Religion	Muslim	29 (34.5)	55 (65.5)	0.462	0.496
	Non-Muslim	14 (41.2)	20 (58.8)
Marital status	Married	2 (12.5)	14 (87.5)	4.580	0.032 ^*
	Unmarried	41 (40.2)	61 (59.8)
Education level	≤Secondary	39 (37.1)	66 (62.9)	0.203	0.652
	> Secondary	4 (30.8)	9 (69.2)
Clinical factors
Duration of illness	≤10 years	13 (46.4)	15 (53.6)	1.581	0.209
	> 10 years	30 (33.3)	60 (66.7)
Age of onset (years)	≤30 years	31 (33)	63 (67)	2.392	0.122
	> 30 years	12 (50)	12 (50)
Types of medications	Atypical	25 (35.7)	45 (64.3)
	Typical	14 (37.8)	23 (62.2)
Combination	4 (36.4)	7 (63.6)	0.047	0.977
Number of relapses	≤5	14 (31.8)	30 (68.2)	0.647	0.421
	> 5	29 (39.2)	45 (60.8)
Employment factors
Employment outcome	Successful	29 (28.4)	73 (71.6)	20.835	< 0.001 ^*
	Unsuccessful	14 (87.5)	2 (12.5)
Types of employment	Competitive	27 (33.8)	53 (63.3)	2.183	0.336
	Smart partnership	5 (31.3)	11 (68.8)
	Social enterprise	11 (50.0)	11 (50.0)
Salary	≤1000	31 (36.9)	53 (63.1)	0.027	0.869
	> 1000	12 (35.3)	22 (64.7)
Getting preferred job	Yes	39 (39.8)	59 (60.2)	2.810	0.094
	No	4 (20.0)	16 (80.0)
Types of job	Manual labour	19 (40.4)	28 (59.6)	1.418	0.492
	Services	17 (30.9)	38 (69.1)
	Others	7 (43.8)	9 (56.3)
Past work history	< 1 month	14 (66.7)	7 (33.3)	10.077	0.002 ^*
	≥1 month	29 (29.9)	68 (70.1)
				t	P
Duration of enrolment (months)	29.72 (16.18)	31.44 (30.23)	–0.345	0.731
Job tenure (months)	19.58 (21.58)	25.09 (33.02)	–0.980	0.329

χ² chi-square and t-test; p < 0.05 as significant at 95% CI.

Multiple logistic regression (Table 5) indicated that the employment outcome (adjusted OR: 12.50; 95% CI: 2.55–61.21; p = 0.002) and past work history (adjusted OR: 3.36; 95% CI: 1.05–10.70; p = 0.041) were the significant predictors of working memory among patients with schizophrenia in supported employment program in this study. These two variables explained 30.2% of the variation of working memory (Nagelkerke R² = 0. 302).

Table 5

Contributing factors for working memory of the patients

Variables	B	p	Adjusted OR	95% CI
Marital status	1.710	0.061	5.531	0.922–33.173
Employment outcome	2.526	0.002	12.498	2.552–61.206
Past work history	1.211	0.041	3.356	1.053–10.700

p-value < 0.05 as significant at 95% CI. The model reasonably fits well. There is no interaction between independent variables and no multicollinearity problem.

4 Discussion

This study indicated that the patients who had successful employment which was defined as working for 40 hours or more in a month were found to have a higher percentage of no impairment in working memory (71.6%), compared with those who were unsuccessful (working for less than 40 hours per month). Our study revealed that patients who had successful employment were 12.5 times more likely to have no impairment in working memory as compared to those with unsuccessful employment. Our findings were supported by previous study which demonstrated that patients who worked more than 30 hours per week (full time) performed better in working memory in contrast with patients who worked less than 30 hours per week (half time) or unemployed (McGurk & Meltzer, 2000). In patients with schizophrenia, intensive activation of under-functioning cognitive systems led to lasting improvements in working memory and further resulted in greater success in work (Wexler & Bell, 2005).

We found other clinical parameters including duration of illness, age of onset of the illness, types of medications, and number of relapses did not give significant impact to the impairment of working memory among our studied patients. Perhaps, the design of this study and selection of sample which exclusively enrolled participants in supported employment program have created selection bias. A meta-analysis on age at onset and cognitive function of patients with schizophrenia suggested that patient with earlier onset of illness have more severe cognitive deficits that persist throughout the course of the disorder (Rajji et al., 2009). In a different meta-analysis, patients with schizophrenia had large deficits across all three working memory domains (phonological, visuospatial, and central executive) but “there was also no consistent association between duration of illness, antipsychotic medication, or symptom profile and working memory in schizophrenia” (Forbes et al., 2009).

While a few researchers were investigating more invasive ways such as transcranial direct current (Impey et al., 2017; Schwippel et al., 2018) or magnetic stimulation (Jiang et al., 2019), and medications [such as newer antipsychotics, including paliperidone, aripiprazole, and ziprasidone; nicotine and its receptor modulators, including varenicline; acetylcholinesterase inhibitors including galantamine; and N-methyl-D-aspartate glutamate receptor (NMDAR) enhancer (Hsu et al., 2018)] to enhance working memory of patients with schizophrenia, our study indicated that by merely continuing job activities, the patients could maintain their functional working memory. Perhaps by continuous sensory stimulation while performing job activities promote activation of sensory memory leading to subsequent stimulation of working memory. Vice versa, substantial studies have indicated good working memory is vital for patients to continue their job and to be productive (McGurk et al., 2018; Metcalfe et al., 2018). In order to enhance further working memory of patients with schizophrenia, a few researchers have added or suggested other interventions such as neurocognitive enhancement therapy (Bell et al., 2007), computerised cognitive training (Subramaniam et al., 2014), and cognitive remediation therapy and working memory training (Lawlor-Savage & Goghari, 2014).

The findings of this research are relevant to inform mental health professionals of the importance of employment for maintaining working memory of patients with schizophrenia. The brain is a complex and efficient organ; hence the interaction of other cognitive elements (including executive functions, social cognition, motivation, attention, and learning) with working memory should not be neglected. In order to provide comprehensive care for patients with schizophrenia, continuous employment should be supported, not only by the clinicians but also the employers. Stigma related to mental illness could be reduced if employers give equal opportunity for patients with schizophrenia to obtain and maintain competitive jobs. Patients with schizophrenia should also receive equal employment benefits such as salary, annual leave, and medical benefits similar with their healthy counterparts. Legal provision to guarantee that patients with schizophrenia have equal employment opportunities should be considered by policy makers in the country. Continuous support from employer, health professionals, and family are prudent to ensure that patients with schizophrenia could maintain their jobs. The findings also support the current paradigm shift in the rehabilitation program for patients with schizophrenia in Malaysia which is moving away from day-care centres and traditional vocational training which used the “train and place” method such as sheltered workshops to supported employment programs around the country. The supported employment program for patients with mental illnesses including those with schizophrenia are currently run by the Community Mental Health Centres (MENTARI) throughout the country. It is hoped that more supported employment programs could be established in Malaysia for patients with schizophrenia which would also include suburban and rural areas in the near future.

5 Conclusion

This study provides insights to the benefit of continuous job activities to the working memory of patients with schizophrenia. The impact of job activities may change not only our participants’ life, as it has thousands of people like them all around the world. Given the potential benefit of supported employment, it is recommended that this program to be implemented as part of routine management for people with severe mental illness such as schizophrenia. Besides providing benefit at individual level, supported employment may indirectly reduce the unemployment rate and increased labour force participation. While at the ground level rehabilitation psychiatrists focus in providing the services, it is crucial for the government to support this program by enhancing policy in management of people with severe mental illness by including supported employment as part of the recommended activities and implementing them. Furthermore, similar interventions may help other people with disabilities such as patients with epilepsy, physical injuries, stroke and other neurological, neuromuscular or skeletal disabilities. Hence, supported employment may be beneficial to be extended to other types of disabilities.

Nevertheless, we would like to inform that the study was limited by its design and suggest a more robust prospective study, using diagnostic assessment and larger sample size to determine the contributing factors for impairment of working memory among patients with chronic mental illness. The full score for working memory could be used for future study to capture the association between the variables of interest and working memory more accurately. We are aware that many other personal, job, and environmental factors could influence their working memory that has not been included in this study. Besides working memory, there are other elements of executive functions (such as inhibitory and self-control, cognitive flexibility, creativity reasoning, problem solving, and planning) which are crucial for independent living of patients with schizophrenia, hence further investigations are recommended.

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

The research was approved by the Research Ethics Committee, Universiti Teknologi MARA (UiTM), Malaysia (Reference number: 600-IRMI (5/1/6)) and the National Medical Research and Ethics Committee (MREC) of the Ministry of Health, Malaysia via the National Medical Research Registry (NMRR) (Registration number: NMRR-17-3366-38938).

Footnotes

Acknowledgments

The authors thank the Director of Hospital Permai, Johore, Malaysia, for allowing them to conduct this study in the mental health institution.

Funding

None to report.

Informed consent

Written informed consent was obtained from all participants.

References

American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). https://doi.org/10.1176/appi.books.9780890425596.

August,

S. M.

, Kiwanuka,

J. N.

, McMahon,

R. P.

, Gold,

J. M.

(2012) The MATRICS Consensus Cognitive Battery (MCCB): Clinical and cognitive correlates. Schizophrenia Research. 134(1), 76–82. https://doi.org/10.1016/j.schres.2011.10.015.

Aziz,

A. A.

, Salina,

A. A.

, Abdul Kadir

A. B.

, Badiah,

, Cheah,

Y. C.

, Nor Hayati

, Ruzanna,

Z. Z.

, Sharifah Suziah

S. M.

, Chee,

K. Y.

(2008) The National Mental Health Registry (NMHR). The Medical Journal of Malaysia. 63(Suppl C), 15–17. .

Baddeley,

(1992) Working memory. Science. 255(5044), 556LP–559. https://doi.org/10.1126/science.1736359.

Bell,

, Bryson,

, Greig,

, Corcoran,

, Wexler,

B. E.

(2001) Neurocognitive enhancement therapy with work therapy: Effects on neuropsychological test performance.. Archives of General Psychiatry. 58(8), 763–768. https://doi.org/10.1001/archpsyc.58.8.763.

Bell,

, Fiszdon,

, Greig,

, Wexler,

, Bryson,

(2007) Neurocognitive enhancement therapy with work therapy in schizophrenia: 6-Month follow-up of neuropsychological performance.. Journal of Rehabilitation Research and Development. 44(5), 761–770. https://doi.org/10.1682/JRRD.2007.02.0032.

Bond,

G. R.

, Drake,

R. E.

, Becker,

D. R.

(2008) An update on randomized controlled trials of evidence-based supported employment.. Psychiatric Rehabilitation Journal. 31(4), 280–290. https://doi.org/10.2975/31.4.2008.280.290 .

Charzyńska,

, Kucharska,

, Mortimer,

(2015) Does employment promote the process of recovery from schizophrenia? A review of the existing evidence. International Journal of Occupational Medicine and Environmental Health. 28(3), 407–418. https://doi.org/10.13075/ijomeh.1896.00341.

Federal Register (2001) State Vocational Rehabilitation Services Program: Final Rules.: U.S. Government Printing Office. 66(11), 4389.

10.

Forbes,

N. F.

, Carrick,

L. A.

, McIntosh,

A. M.

, Lawrie,

S. M.

(2009) Working memory in schizophrenia: A meta-analysis. In Psychological Medicine. 39(6), 889–905. https://doi.org/10.1017/S0033291708004558.

11.

Frederick,

D. E.

, VanderWeele,

T. J.

(2019) Supported employment: Meta-analysis and review of randomized controlled trials of individual placement and support. PLoS ONE. 14(2), 1–26. https://doi.org/10.1371/journal.pone.0212208.

12.

Green,

M. F.

(2006) Cognitive impairment and functional outcome in schizophrenia and bipolar disorder. The Journal of Clinical Psychiatry. 67(10), e12.

13.

Harvey,

P. D.

, Ph,

, Keefe,

R. S. E.

(2001) Reviews and overviews schizophrenia following novel antipsychotic treatment. Psychiatry: Interpersonal and Biological Processes, February, 176-184.

14.

Hsu,

W. Y.

, Lane,

H. Y.

, Lin,

C. H.

(2018) Medications used for cognitive enhancement in patients with schizophrenia, bipolar disorder, Alzheimer’ disease, and Parkinson's disease. Frontiers in Psychiatry.https://doi.org/10.3389/fpsyt.2018.00091

15.

Impey,

, Baddeley,

, Nelson,

, Labelle,

, Knott,

(2017) Effects of transcranial direct current stimulation on the auditory mismatch negativity response and working memory performance in schizophrenia: A pilot study. Journal of Neural Transmission (Vienna, Austria: 1996). 124(11), 1489–1501.https://doi.org/10.1007/s00702-017-1783-y.

16.

Jiang,

, Guo,

, Xing,

, He,

, Peng,

, Du,

, McClure,

M. A.

, Mu,

(2019) Effects of high-frequency transcranial magnetic stimulation for cognitive deficit in schizophrenia: A meta-analysis. Frontiers in Psychiatry. 10(MAR), 1–11. https://doi.org/10.3389/fpsyt.2019.00135.

17.

Keefe,

R. S. E.

, Fenton,

W. S.

(2007) How should DSM-V criteria for schizophrenia include cognitive impairment?Schizophrenia Bulletin. 33(4), 912–920. https://doi.org/10.1093/schbul/sbm046.

18.

Kern,

R. S.

, Nuechterlein,

K. H.

, Green,

M. F.

, Baade,

L. E.

, Fenton,

W. S.

, Gold,

J. M.

, Keefe,

R. S. E.

, Mesholam-Gately,

, Mintz,

, Seidman,

L. J.

, Stover,

, Marder,

S. R.

(2008) The MATRICS Consensus Cognitive Battery, part 2: Co-norming and standardization. American Journal of Psychiatry. 165(2), 214–220. https://doi.org/10.1176/appi.aj2007.07010043.

19.

Kinoshita,

, Ta,

, Kinoshita,

, Honyashiki,

, Im,

, Marshall,

, Gr,

, Huxley,

, Kinoshita,

, Ta,

, Kinoshita,

, Honyashiki,

, Im,

, Marshall,

, Gr,

, Huxley,

, Amano,

, Kingdon,

(2013) Schizophrenia can and should be renamed. BMJ. 2007;334, 221–2. https://doi.org/10.1002/14651858.CD008297.pub2.www.cochranelibrary.com.

20.

Lawlor-Savage,

, Goghari,

V. M.

(2014) Working memory training in schizophrenia and healthy populations. Behavioral Sciences. 4(3), 301–319. https://doi.org/10.3390/bs4030301.

21.

Lystad,

J. U.

, Falkum,

, Mohn,

, Haaland,

V. Ø.

, Bull,

, Evensen,

, Rund,

B. R.

, Ueland,

(2014) The MATRICS Consensus Cognitive Battery (MCCB): Performance and functional correlates. Psychiatry Research. 220(3), 1094–1101. https://doi.org/10.1016/j.psychres.2014.08.060.

22.

Marshall,

, Goldberg,

R. W.

, Braude,

, Dougherty,

R. H.

, Daniels,

A. S.

, Ghose,

S. S.

, George,

, Delphin-Rittmon,

M. E.

(2014) Supported employment: Assessing the evidence. Psychiatric Services. 65(1), 16–23. https://doi.org/10.1176/appi.ps.201300262.

23.

McGurk,

S. R.

, Meltzer,

H. Y.

(2000) The role of cognition in vocational functioning in schizophrenia. Schizophrenia Research. 45(3), 175–184. https://doi.org/10.1016/s0920-9964(99)00198-x.

24.

McGurk,

S. R.

, Drake,

R. E.

, Xie,

, Riley,

, Milfort,

, Hale,

T. W.

, Frey,

(2018) Cognitive predictors of work among social security disability insurance beneficiaries with psychiatric disorders enrolled in IPS supported employment. Schizophrenia Bulletin. 44(1), 32–37. https://doi.org/10.1093/schbul/sbx115.

25.

Medical Development Division Ministry of Health Malaysia (2011) Psychiatric and mental health services operational policy. 124. https://www.moh.gov.my/images/gallery/Polisi/PSYCHIATRYOPERATIONALPOLICY.pdf.

26.

Metcalfe,

J. D.

, Riley,

, McGurk,

, Hale,

, Drake,

R. E.

, Bond,

G. R.

(2018) Comparing predictors of employment in Individual Placement and Support: A longitudinal analysis. Psychiatry Research. 264, 85–90. https://doi.org/https://doi.org/10.1016/j.psychres.2018.03.050.

27.

Midin,

, Razali,

, ZamZam,

, Fernandez,

, Hum,

L. C.

, Shah,

S. A.

, Radzi,

R. S. M.

, Zakaria,

, Sinniah,

(2011) Clinical and cognitive correlates of employment among patients with schizophrenia: A cross-sectional study in Malaysia. International Journal of Mental Health Systems. 5(1), 14. https://doi.org/10.1186/1752-4458-5-14.

28.

Normala,

, Abdul Hamid

A. R.

, Shamsul Azhar

(2009) Neuro-cognitive performance in patients with schizophrenia: A cross-sectional study in a psychiatric clinic of a University Hospital. Journal of Medicine and Health Sciences. 5(1), 21–30.

29.

Nuechterlein,

K. H.

, Green,

M. F.

, Kern,

R. S.

, Baade,

L. E.

, Barch,

D. M.

, Cohen,

J. D.

, Essock,

, Fenton,

W. S.

, Frese,

F. J.

, Gold,

J. M.

, Goldberg,

, Heaton,

R. K.

, Keefe,

R. S. E.

, Kraemer,

, Mesholam-Gately,

, Seidman,

L. J.

, Stover,

, Weinberger,

D. R.

, Young,

A. S.

, Marder

S. R.

(2008) The MATRICS consensus cognitive battery, part 1: Test selection, reliability, and validity. American Journal of Psychiatry. 165(2), 203–213. https://doi.org/10.1176/appi.ajp.2007.07010042.

30.

Nuechterlein,

K. H.

, Subotnik,

K. L.

, Green,

M. F.

, Ventura,

, Asarnow,

R. F.

, Gitlin,

M. J.

, Yee,

C. M.

, Gretchen-Doorly,

, Mintz,

(2011) Neurocognitive predictors of work outcome in recent-onset schizophrenia.. Schizophrenia Bulletin. 37(SUPPL. 2), 33–40. https://doi.org/10.1093/schbul/sbr084.

31.

Rajji,

T. K.

, Ismail,

, Mulsant,

B. H.

(2009) Age at onset and cognition in schizophrenia: Meta-analysis.. British Journal of Psychiatry. 195(4), 286–293. https://doi.org/10.1192/bjp.bp.108.060723.

32.

Reichenberg,

(2010) The assessment of neuropsychological functioning in schizophrenia. Dialogues in Clinical Neuroscience. 12(3), 383–392. https://doi.org/10.31887/DCNS.2010.12.3/areichenberg.

33.

Schwippel,

, Papazova,

, Strube,

, Fallgatter,

A. J.

, Hasan,

, Plewnia,

(2018) Beneficial effects of anodal transcranial direct current stimulation (tDCS) on spatial working memory in patients with schizophrenia. European Neuropsychopharmacology: The Journal of the European College of Neuropsychopharmacology. 28(12), 1339–1350. https://doi.org/10.1016/j.euroneuro.2018.09.009.

34.

Sheehan,

D. V.

, Lecrubier,

, Sheehan,

K. H.

, Amorim,

, Janavs,

, Weiller,

, Hergueta,

, Baker,

, Dunbar,

G. C.

(1998) The Mini-International Neuropsychiatric Interview (M.I.N.I.): The development and validation of a structured diagnostic psychiatric interview for DSM-IV and ICD-10. Journal of Clinical Psychiatry. 59(SUPPL. 20), 22–33. https://doi.org/10.1016/S0924-9338(99)80239-9.

35.

Subramaniam,

, Luks,

T. L.

, Garrett,

, Chung,

, Fisher,

, Nagarajan,

, Vinogradov,

(2014) Intensive cognitive training in schizophrenia enhances working memory and associated prefrontal cortical efficiency in a manner that drives long-term functional gains. NeuroImage. 99, 281–292. https://doi.org/10.1016/j.neuroimage.2014.05.057.

36.

Wexler,

B. E.

, Bell,

M. D.

(2005) Cognitive remediation and vocational rehabilitation for schizophrenia. Schizophrenia Bulletin. 31(4), 931–941. https://doi.org/10.1093/schbul/sbi038.

	Impairment of working memory
Variables	Yes n (%)	No n (%)	χ ²	p
Socio-demographic factors
Age (years)	≤45	24 (31.6)	52(68.4)	2.179	0.140
	> 45	19 (45.2)	23 (54.8)
Gender	Male	31 (33.3)	62 (66.7)	1.830	0.176
	Female	12 (48.0)	13 (52.0)
Ethnicity	Malay	29 (35.8)	52 (64.2)	0.045	0.831
	Non-Malay	14 (37.8)	23 (62.2)
Religion	Muslim	29 (34.5)	55 (65.5)	0.462	0.496
	Non-Muslim	14 (41.2)	20 (58.8)
Marital status	Married	2 (12.5)	14 (87.5)	4.580	0.032 ^*
	Unmarried	41 (40.2)	61 (59.8)
Education level	≤Secondary	39 (37.1)	66 (62.9)	0.203	0.652
	> Secondary	4 (30.8)	9 (69.2)
Clinical factors
Duration of illness	≤10 years	13 (46.4)	15 (53.6)	1.581	0.209
	> 10 years	30 (33.3)	60 (66.7)
Age of onset (years)	≤30 years	31 (33)	63 (67)	2.392	0.122
	> 30 years	12 (50)	12 (50)
Types of medications	Atypical	25 (35.7)	45 (64.3)
	Typical	14 (37.8)	23 (62.2)
Combination	4 (36.4)	7 (63.6)	0.047	0.977
Number of relapses	≤5	14 (31.8)	30 (68.2)	0.647	0.421
	> 5	29 (39.2)	45 (60.8)
Employment factors
Employment outcome	Successful	29 (28.4)	73 (71.6)	20.835	< 0.001 ^*
	Unsuccessful	14 (87.5)	2 (12.5)
Types of employment	Competitive	27 (33.8)	53 (63.3)	2.183	0.336
	Smart partnership	5 (31.3)	11 (68.8)
	Social enterprise	11 (50.0)	11 (50.0)
Salary	≤1000	31 (36.9)	53 (63.1)	0.027	0.869
	> 1000	12 (35.3)	22 (64.7)
Getting preferred job	Yes	39 (39.8)	59 (60.2)	2.810	0.094
	No	4 (20.0)	16 (80.0)
Types of job	Manual labour	19 (40.4)	28 (59.6)	1.418	0.492
	Services	17 (30.9)	38 (69.1)
	Others	7 (43.8)	9 (56.3)
Past work history	< 1 month	14 (66.7)	7 (33.3)	10.077	0.002 ^*
	≥1 month	29 (29.9)	68 (70.1)
				t	P
Duration of enrolment (months)	29.72 (16.18)	31.44 (30.23)	–0.345	0.731
Job tenure (months)	19.58 (21.58)	25.09 (33.02)	–0.980	0.329