Negative symptoms are present in the psychosis prodrome. However, the extent to which these symptoms are present prior to the onset of the first episode of psychosis remains under-researched. The goal of this study is to examine negative symptoms in a sample of individuals at clinical high risk (CHR) for psychosis and to determine if they are predictive of conversion to psychosis. Participants (n = 138) were all participants in the North American Prodrome Longitudinal Study (NAPLS 1) project. Negative symptoms were assessed longitudinally using the Scale of Prodromal Symptoms. The mean total negative symptom score at baseline was 11.0, with 82.0% of the sample scoring at moderate severity or above on at least one negative symptom. Over the course of 12 months, the symptoms remained in the above moderate severity range for 54.0% of participants. Associations between individual symptoms were moderate, and a factor analysis confirmed that all negative symptoms loaded heavily on one factor. Negative symptoms were more severe and persistent overtime in those who converted to psychosis, significantly predicting the likelihood of conversion. Thus, early and persistent negative symptoms may represent a vulnerability for risk of developing psychosis.
Recent advances in research in early detection of psychosis have led to the development of reliable criteria to identify individuals who may be at risk of developing psychosis and thus potentially experiencing a prodrome for psychosis (Yung and McGorry, 1996b and McGlashan et al., 2010). These prospective studies rely primarily on the presence of attenuated positive symptoms and decreased functioning (Yung and McGorry, 1996b and McGlashan et al., 2010). However, significant proportions of these individuals have non-specific symptoms (e.g. depression and anxiety) as well as negative symptoms, such as social isolation/withdrawal, and reduced motivation (Lencz et al., 2004). This finding pertaining to the construct of amotivation or avolition is in agreement with findings from patients with schizophrenia (Faerden et al., 2009). Interestingly, it is these behavioural and functional changes that are often the first reasons for seeking help (Yung and McGorry, 1996a and Lencz et al., 2004). Relative to attenuated positive symptoms, the prevalence of negative symptoms is high (Yung et al., 2003, Lencz et al., 2004 and Velthorst et al., 2009), among of which social isolation and deterioration in role (school) functioning are most frequently reported (Lencz et al., 2004). Furthermore, negative symptoms, especially increased social isolation and withdrawal, have been reported to be predictive of transition to psychosis (Kwapil, 1998, Mason et al., 2004, Yung et al., 2005 and Velthorst et al., 2009). In the Edinburgh longitudinal study of individuals at genetic high risk of psychosis (Johnstone et al., 2005), social withdrawal and isolation, as measured on the Structural Interview for Schizotypy, emerged as the strongest discriminator between those who converted and those who did not.
Typically, negative symptoms are examined as one construct, although there are reports of negative symptoms clustering into two domains of diminished expression (i.e. affective flattening and poverty of speech) and amotivation (i.e. avolition/apathy and anhedonia/asociality) (Mueser et al., 1994 and Sayers et al., 1996). More recently there has been a focus on differences among individual negative symptoms with suggestions that “avolition” is a core negative symptom with a direct impact on both functional outcome and cognitive function (Foussias and Remington, 2010).
Previous studies of the psychosis prodrome that explored the predictive value of negative symptoms to psychosis conversion have done so using different instruments to assess prodromal symptoms. Whereas some studies used scales designed to rate the severity of sub-psychotic level symptoms (Yung et al., 2005 and Velthorst et al., 2009) others used conventional rating scales for psychotic-level symptoms (Mason et al., 2004) or a scale designed to assess a single symptom (Kwapil, 1998). Furthermore, none of the studies included longitudinal examination of negative symptoms. Thus, the goal of the present investigation was to examine in more detail negative symptoms in a sample of individuals described as being at clinical high risk (CHR) of developing psychosis. The specific aims were: 1) to determine the prevalence of individual negative symptoms; 2) to determine the stability of negative symptoms, 3) to explore the factor structure of positive and negative symptoms of the SOPS, and 4) to explore longitudinally the role of negative symptoms in conversion to psychosis.
