Greater Apathy Associated With Selective Serotonin Reuptake Inhibitor Use in Parkinson's Disease.

Objective: Apathy, a motivational disorder, is common in Parkinson's disease (PD) and often misdiagnosed as depression. Use of selective serotonin reuptake inhibitors (SSRIs) has been associated with increased apathy in adolescents and adults with depression. Based on observations that serotonin may downregulate dopaminergic systems, we examined the relationship between apathy and SSRI use in individuals with PD.

Methods: Medications, mood/motivation scales, and clinical data were collected from a convenience sample of 400 individuals with PD. Depression and apathy were measured using the Beck Depression Inventory-II (BDI-Il) and the Apathy Scale (AS). Antidepressant medications were grouped by mechanism type.

Results: Of the 400 PD patients, 26% were on SSRIs. On standard mood/motivation scales, 38% of the sample exceeded clinical cut-offs for apathy and 28% for depression. Results of hierarchical regression analyses revealed that SSRIs were the only antidepressant that were significantly associated with higher apathy scores (β = .1, P = .02). Less education (β = -.1, P = .01) worse cognition (β = -.1, P = .01), and greater depressive symptoms (β = .5, P < .001) were also significant predictors of apathy.

Conclusion: These findings suggest that use of SSRIs, but not other antidepressants, is associated with greater apathy in PD. Given the interactive relationship between serotonin and dopamine, the current findings highlight the importance of considering apathy when determining which antidepressants to prescribe to individuals with PD. Similarly, switching a SSRI for an alternative antidepressant in individuals with PD who are apathetic may be a potential treatment for apathy that needs further study.