Although most efforts to examine behavioral deficits in schizophrenia have focused on neurocognition, the past 25 years have seen a growing literature on emotion perception deficits in schizophrenia (reviews by Edwards et al,1
Mandal et al,2
and Morrison et al3
) and in the larger domain of social cognition,4,5
which is defined as the ability to process and apply social information. Recognition of facial expressions of emotions is instrumental constituent of nonverbal communication, and several studies in schizophrenia have underscored that emotion perception abilities are related to social competence6–10
and predict later work functioning and independent living.11
In addition, emotion perception is more affected in schizophrenia compared with psychiatric control groups, such as mood disorders.12–14
Reviews of early studies3
showed that results were limited by small sample sizes consisting of mostly inpatients with prolonged hospitalizations and the use of diverse nonstandardized stimuli. Study designs improved considerably in the 1990s1,2
with employment of standardized tasks, exclusion criteria, and inclusion of in- and outpatient groups that with respect to demographic and clinical characteristics are more representative of schizophrenia. The qualitative review by Edwards et al1
of studies published prior to 2000 details the need to attend to numerous demographic, task, and illness-related variables that can interfere with accurate emotion perception. Among others, duration of illness, negative symptoms, medication levels, outpatient vs inpatient status, stage of illness, and schizophrenia subtypes were identified as potential and unexamined variables that contribute to emotion perception impairment and warrant further attention.
In general, task designs within emotion perception studies can be separated into those that focus on identification of specific emotions and those that differentiate between intensities of emotion expressions. Identification tasks rely on choosing a qualitative label, usually from a limited number of choices, to the picture of a facial expression. Differentiation tasks require judgment regarding differences in emotion expressions—typically of 2 visual stimuli—without necessary identification of the emotion. Numerous studies have employed both identification and differentiation tasks, based on the possibility that the different tasks yield differential impairment. While early investigations included nonstandardized emotional stimuli, many subsequent studies employed face stimuli developed by Ekman and Friesen15
or Gur et al.16
The black and white stimuli created by Ekman and Friesen15
consist of posed facial expressions of universally recognized emotions, including happiness, sadness, anger, fear, disgust, and surprise. Pictures are of mostly middle-aged Caucasian posers, with more recent inclusion of Asian but not African American or Hispanic posers. The stimuli of Gur et al16
include color faces expressing happy, sad, angry, fearful, and disgusted emotions in posed and evoked conditions, across adult age groups and different ethnicities. Very few studies have failed to elucidate emotion impairment in schizophrenia, and the argument has been made that methodology and task design, rather than emotion perception abilities, may account for group differences seen.17
, but not all,17,23
cross-sectional studies have shown an association between illness severity, positive and negative symptoms of schizophrenia, and emotion perception abilities that may be further medicated by chronicity of illness.8
Potentially, the issue between clinical parameters and perception abilities can be more decisively investigated in a longitudinal design. Several studies12,24–26
with short-term follow-up in acutely ill patients have revealed that standard treatment, including antipsychotics, and resultant response do not appreciably improve performance on emotion perception suggesting a trait-like deficit. On the other hand, specific application of emotion remediation has been found to be beneficial.27
While the vast majority of studies on facial emotion perception establish the existence of impairment in schizophrenia, potential factors related to task design and sample characteristics that may influence published findings remain to be better understood. We conducted a comprehensive meta-analysis of the existing studies on emotion perception in schizophrenia with the aim to quantify the magnitude of deficit seen in facial emotion perception and to identify variables that may moderate the impairment in schizophrenia. Specifically, the selection of variables was based on (1) the majority of facial emotion perception studies being based on tasks of emotion identification or differentiation, (2) findings in the existing literature that implicate certain clinical variables, ie, symptoms, hospitalization status, and illness duration with emotion perception abilities, (3) findings in the existing literature that implicate certain demographic variables, ie, age, gender, ethnicity, with emotion perception abilities, and (4) adequate representation of the potential variables within the extant literature to allow for meaningful comparisons.
Because most studies that employed tasks that measured emotion identification or differentiation reported on emotion perception in general, we did not anticipate finding a differential effect related to task. The lack of test design affecting performance may indicate that although the task types may overlap with different aspects of cognition, emotion identification and differentiation tasks tap the general domain of facial emotion perception to a similar extent.
We examined relatedness for clinical factors, in particular diagnosis of schizophrenia vs inclusion of schizoaffective disorder, hospitalization status, duration of illness, and clinical symptoms, and we anticipated that emotion perception deficits in schizophrenia show association with characteristic clinical symptoms but are not clearly related to diagnosis, stabilization of psychosis, or to deterioration with prolonged duration of illness. Similarly, based on the limited effect of antipsychotics on cognition, we did not expect the meta-analysis to reveal clear effects associated with antipsychotic treatment, ie, related to being on antipsychotic and type and dosage.
Studies that have described demographic factors associated with emotion perception were performed on large sample sizes. In healthy controls, subtle effects of age, gender, and race have been associated with perception ability.28–31
Considering group characteristics that commonly included age ranges between 18 and 65 years, male predominance, and limited inclusion of participants with different ethnicities, we were not confident to find a clear association between emotion perception and demographics between and within groups. Nevertheless, investigation of demographic characteristics may prove informative in elucidating that the effect of the clinical condition on emotion perception outweighs demographic influences.