Apathy alters emotional arousal in chronic schizophrenia

Abstract

Background: Within the heterogeneity of schizophrenia, apathy constitutes an independent cluster of negative symptoms associated with poor outcomes. Attempts to identify an emotional deficit in patients who have schizophrenia with negative symptoms have yielded mixed results, and studies that focus on the relationship between apathy and emotional disorders are lacking.

Methods: We set out to remedy this shortcoming using a validated battery of film excerpts to induce positive and negative emotions in patients with chronic schizophrenia with (n = 20) or without (n = 20) apathy, and in controls (n = 20) comparable for age, sex and socioeconomic status. We assessed emotions using an innovative but validated technique to evaluate tonic and phasic electrodermal activity and subjective feelings using a standardized visual analogue scale.

Results: Using a qualitative measure of apathy, we did not find a specific decrease in tonic activity during the induction of positive emotions. However, we did observe that patients with apathy showed reduced tonic activity independent of valence (i.e., for both positive and negative emotions) compared with controls and patients without apathy. Moreover, the quantitative measure of apathy (Apathy Evaluation Scale) was the only significant factor, explaining 24% of the variance in tonic activity during induction of positive emotions after controlling for confounding factors.

Limitations: Electrodermal activity was the only physiologic measure we acquired. We induced several emotions sequentially that might have overlapped with each other, but we added an emotional “washout” period and randomized the order of each film excerpt to limit this possibility.

Conclusion: Taken together, these results suggest that apathy in schizophrenia could impair tonic activity during positive emotions. Treatments aimed at enhancing positive emotions may help alleviate apathy in schizophrenia.

Fig. 1

Procedure for emotional induction. First, we performed a calibration of EDA measures using a period of relaxation. Then, we ran 5 cycles using 5 different film excerpts that targeted 5 emotions in random order, with continuous recording of EDA. Each cycle began with a relaxation procedure (3 min), followed by acquisition of a baseline EDA value and a first subjective emotional rating using the DES. Then, a target emotion was induced using a film excerpt. We used the final minute of the film excerpt for EDA processing, and then a second subjective emotional rating (DES) was performed. DES = Differential Emotion Scale; EDA = electrodermal activity.

Fig. 2

Tonic EDA (μS) in each group during positive and negative film excerpts. Error bars represent standard error of the mean. EDA = electrodermal activity; Scz-A = schizophrena with apathy; Scz-NA = schizophrenia without apathy.

Fig. 3

Decreased tonic EDA (μS) during the positive film excerpt was associated with higher AES scores. Controlling variables were chlorpromazine equivalents, executive dysfunction and positive PANSS score; β was the standardized estimated coefficient for the AES score. AES = Apathy Evaluation Scale; EDA = electrodermal activity; PANSS = Positive and Negative Syndrome Scale.