Deep brain stimulation (DBS) for Parkinson’s disease (PD) is a neurosurgical procedure that involves implanting an electrode stimulator in subcortical structures. Qualitative literature has identified that DBS candidates are concerned about unwanted alterations in personality or sense-of-self following DBS. Furthermore, the reversible nature of DBS has sparked innovation and exploratory treatment options for other conditions, including obsessive-compulsive disorder, substance use, obesity, depression, epilepsy, and chronic pain. Accordingly, this study aimed to quantify the effects of DBS for PD on personality to inform risk-factors of the procedure. We hypothesized participants would endorse mostly non-significant changes in personality following DBS, with significant increases in self-control.

Eight DBS recipients completed routine pre- and post-surgical neuropsychological assessment. They were predominantly male (62.5%), White (93.8%), and college-educated (50%), averaging 68.2 years of age and 10 years of disease duration at post-surgical data collection. All DBS recipients underwent stimulator placement at the subthalamic nucleus, most bilaterally (87.5%). Most participants maintained cognitive functioning at or below the threshold of mild neurocognitive impairment (87.5%); one participant met criteria for PD dementia at post-surgical neuropsychological evaluation.

Participants completed the Severity Indices of Personality Problems: Short Form (SIPP-SF) at pre/post neuropsychological testing. The 60-item self-report questionnaire generates five personality domain scores (Self-Control, Identity Integration, Responsibility, Relational Capacities, Social Concordance) and prorates seven facets from the 118-item SIPP (Emotion Regulation, Responsible Industry, Trustworthiness, Intimacy, Enduring Relationships, Aggression Regulation, Respect).

Two-tail paired-samples t-tests revealed no significant changes between pre- and post-surgical self-report across the five SIPP-SF personality domains and seven prorated facets (p = .173 - .957). The results were consistent with the first hypothesis, but not with the second hypothesis that Self-Control would significantly increase post-surgically (p = .219). In the context of non-significant changes, nearly all personality domains and facets demonstrated modest increases in adaptive personality functioning (mean within person change = 0.88T – 3.06T) with moderate effect sizes observed in Self-Control, Identity Integration, Relational Capacities, Emotion Regulation, and Enduring Relationships (d = .39 - .54).

These results align with earlier quantitative studies of DBS and personality but contradict the adverse changes patients have reported in qualitative and phenomenological studies. In fact, this sample reported modest improvements on most personality scales. Improvements in PD symptoms (e.g., tremors, dyskinesia) after DBS may increase daily functioning and independence, resulting in periphery improvement in aspects of personality functioning.

Despite evidence suggesting personality integrity following DBS, fear of personality change is a common experience of surgical candidates. Future studies using larger and more diverse samples are needed for patients and providers to make more informed decisions regarding treatment, integrating data-driven cost-benefit analyses about the procedure. If providers can cite research to ease fears of identity changes as they do with other neurologic risk factors such as brain bleeds, stroke, and death, additional candidates may choose to undergo the potentially life-altering treatment. As DBS is explored for treatment of increasingly diverse conditions, it is crucial that providers and patients are equipped with robust and evidence-based knowledge regarding the holistic impact of DBS.