The data presented above suggest 2 subdomains of negative symptoms: (1) diminished expression, consisting of affective flattening and poverty of speech, and (2) amotivation, consisting of avolition/apathy and anhedonia/asociality. Other symptoms such as inappropriate affect, poverty of content of speech, and attentional impairment appear to be more closely related to cognitive dysfunction rather than negative symptoms. This is not unlike the present approach outlined in the MATRICS initiative, which distinguishes between 2 classes of subscales: (1) anhedonia/avolition/apathy and (2) blunted affect/alogia. In short, one category speaks to issues of involvement with the surrounding environment (ie, drive and pleasure), while the other addresses an expressive component (ie, affect and speech). However, the relationship between these subdomains or, in fact, the features within each remain in question. Further, do individuals with schizophrenia suffer from hedonic or motivational deficits?
Closer inspection of the subdomains of negative symptoms reveals some interesting relationships. In addition to highlighting 2 subdomains of negative symptoms, these same studies have demonstrated that these 2 subdomains exhibit a moderate interrelationship (interfactor correlation coefficients between 0.47 and 0.57).32,34,52
An examination of the separate subscales of the SANS also noted moderate interrelationships for affective flattening with avolition-apathy and anhedonia-asociality subscales (r
0.49 and 0.48, respectively), as well as for alogia with avolition-apathy and anhedonia-asociality subscales (r
0.61 and 0.53, respectively).31
These findings suggest that the negative symptom domains and symptoms that comprise them, although distinct phenomenological entities, may reflect a common underlying process.
Anhedonia, often identified as a feature of schizophrenia, has been defined as a diminished capacity to experience pleasant emotions55
or, alternatively, difficulty in experiencing interest or pleasure.3
Current evidence from experimental paradigms using diverse emotion-eliciting stimuli, including films, pictures, sounds, and drinks, indicates individuals with schizophrenia report intact experiences of both pleasant and unpleasant emotions in the moment with at least equal intensity compared with healthy controls.56–60
This is true in spite of their diminished capacity for outward expression of emotion and regardless of medication status. Similar results have been obtained in comparisons of deficit and nondeficit schizophrenia with healthy controls, where there was no significant reduction in the experience of emotion, despite a reduction in emotional expressivity in individuals with deficit schizophrenia.61
These findings suggest that individuals with schizophrenia, despite impairments in outward emotional expression, do not have deficits in the internal experience of emotions. That is, they do not appear to have a hedonic deficit, as implied by the terminology used in commonly accepted definitions and rating scales for negative symptoms.
A recent review of the anhedonia construct in schizophrenia by Horan et al (2006)62
also highlights some of the issues contributing to the difficulties in distinguishing anhedonia from amotivation in patients with schizophrenia. With the SANS being the current standard for quantifying negative symptoms, the authors note that the anhedonia/asociality ratings are not only based solely on patients’ capacity to experience pleasant emotions but also on the frequency, quality, and level of interest and engagement in recreational and social activities, therefore measuring several conceptually distinct processes. While decreased interest and engagement in such activities are possible consequences of anhedonia, they may also be the result of various other emotional, motivational, and social factors. Thus, by incorporating actual performance measures, this scale may reflect a social performance deficit more than a fundamental hedonic capacity deficit.62
The concept of anhedonia in schizophrenia, supported by numerous studies over the past 25 years, has been based largely on results using the Chapman physical and social anhedonia scales.62
The majority of these studies have revealed elevated levels of self-reported anhedonia in individuals with schizophrenia, including both social and physical anhedonia in deficit compared with nondeficit schizophrenia,63
while studies using these and other measures of anhedonia have revealed mixed results.62,64
However, there have been concerns about the construct and discriminant validity of the Chapman physical and social anhedonia scales.65–68
These studies raise questions about the underlying construct that is measured by the scales, ie, whether they measure hedonic capacity. Given that much of the support for hedonic deficits in schizophrenia is based on findings using these scales, as well as the contradictory findings between these trait measures of anhedonia and experimental paradigms that have shown intact hedonic capacity,56–58
the presence of anhedonia in this illness remains questionable.
Further examination in schizophrenia of the discrepancy between self-reported trait measures of diminished experience of pleasure and the aforementioned objective findings of intact abilities to experience emotions in the moment suggests that there may be separable components of pleasure. Horan et al (2006)62
draw attention to Klein's (1984)69
distinction between anticipatory pleasure (ie, pleasure derived from anticipating that an activity will be enjoyable) and consummatory pleasure (ie, pleasure derived from engaging in enjoyable activities). Further work in this area by the same group has revealed that patients with schizophrenia, compared with healthy controls, report lower anticipatory pleasure but similar consummatory pleasure.70
In particular, those with schizophrenia report significantly less anticipatory pleasure for goal-directed activities (making dinner, doing errands, working/studying) vs non–goal-directed activities (eating, watching TV, smoking, sleeping). Patients were also significantly less often engaged in goal-directed activities compared with controls; further to this point, anticipatory pleasure scale scores were significantly correlated with clinical ratings of anhedonia and impaired community functioning.70
Recent work by Heerey and Gold (2007)58
has also provided some insight into the experiential and motivational deficits in schizophrenia through exploration of the coupling of affective experience and behavior. Using an experimental paradigm assessing self-reported ratings of pleasure and arousal, as well as degree of effort exerted to seek or avoid exposure to slides of varying affective valence in the present and future, several interesting findings emerged. Individuals with schizophrenia exhibit deficits in their ability to couple their behavior to the motivational properties of a stimulus despite equivalent subjective in the moment pleasantness and arousal ratings for these stimuli compared with healthy controls. Furthermore, significant correlations were noted between these deficits and working memory impairment, particularly for those situations requiring the maintenance of an internal representation for the stimulus. The authors conclude that motivational deficits in schizophrenia reflect impairment in the ability to translate experience into action.
Returning to our question, current evidence suggests that individuals with schizophrenia do not have a hedonic deficit in the strictest sense. Rather, it seems that they experience a diminished capacity to anticipate that pursuit or achievement of a goal will be pleasurable, in addition to impairment in the translation of subjective experience into action, with a resultant decrease in goal-directed behavior. This concept of anticipatory pleasure has been suggested to be more closely related to motivation and goal-directed behavior,69
as well as to the concept of “wanting.”71
Overall, these findings suggest that individuals with schizophrenia experience amotivation rather than anhedonia. Moreover, the interrelationship between diminished expression and amotivation suggests that these subdomains of symptoms may represent differential expressions of a common underlying process.