Antipsychotics and amotivation

Abstract

Antipsychotic drugs are thought to produce secondary negative symptoms, which can also exacerbate primary negative symptoms. In the present study, we examined whether motivational deficits in particular were related to antipsychotic treatment in patients with schizophrenia in a dose-dependent manner. Five hundred and twenty individuals with schizophrenia who were receiving antipsychotic monotherapy for at least 6 months and followed prospectively were included in the present study. Participants were receiving one of five antipsychotic medications (olanzapine, perphenazine, quetiapine, risperidone, or ziprasidone), and analyses were conducted for patients receiving each drug separately. Analysis of covariance models were constructed to examine the effect of antipsychotic dose on level of motivational impairment, controlling for selected demographic and clinical variables (eg, positive symptoms). Level of motivation, or deficits therein, were evaluated using a derived measure from the Quality of Life Scale, and in addition with scores derived from the Positive and Negative Syndrome Scale. Antipsychotic dose was not related to the level of amotivation for any of the medications examined. Moreover, severity of sedation was not significantly related to the degree of amotivation. One hundred and twenty-one individuals were identified as antipsychotic-free at baseline, and after 6 months of antipsychotic treatment, no change in motivation was found. Chronic treatment with antipsychotics does not necessarily impede or enhance goal-directed motivation in patients with schizophrenia. It is possible that the negative impact of antipsychotics in this regard is overstated; conversely, the present results also indicate that we must look beyond antipsychotics in our efforts to improve motivation.

Trial registration: ClinicalTrials.gov NCT00014001.

Figure 1

Level of motivation stratified by dose for each antipsychotic drug: (a) olanzapine, (b) perphenazine, (c) quetiapine, (d) risperidone, and (e) ziprasidone. Higher score on this measure denote greater motivation, or less deficits therein. Error bars denote standard deviations.

Figure 2

Level of social amotivation stratified by dose for each antipsychotic drug: (a) olanzapine, (b) perphenazine, (c) quetiapine, (d) risperidone, and (e) ziprasidone. Higher score on this measure denote greater severity of motivational deficits. Error bars denote standard deviations.

Figure 3

Change in the level of motivation from an antipsychotic-free state (baseline), and after 6 months of antipsychotic treatment (follow-up). (a) Level of motiation as measured by the Quality of Life Scale is plotted, where higher scores denote greater motivation. (b) Level of social amotiation as measured by the Positive and Negative Syndrome Scale is plotted, where higher scores denote greater amotivation, or less motivation. Error bars reflect standard error of the mean.