Long-Term Lithium Treatment and Sensory Processing Sensitivity in Bipolar Disorder Patients

Sensory processing sensitivity (SPS) describes innate temperament, which consists of three characteristics: ease of excitation (EOE), low sensory threshold (LST), and aesthetic sensitivity (AES). There has been no research on SPS in bipolar disorder (BD), nor the effect of treatment on these traits. Relations between temperament, personality, and the course of BD are complex and modify the effect of treatment. Long-term lithium treatment modifies course of the illness and excellent lithium responders are known from their unique clinical characteristic. The aim of the study was to examine the relation between pharmacological treatment and SPS in BD patients.

The study group comprised 35 patients (F/M = 26/9) with BD, where 20 patients were diagnosed with BD type I and 15 patients with BD type II. Twenty patients were treated with lithium (16 ± 13 years) and fifteen with other mood stabilizers (14 ± 4 years). The comparison between groups included parameters: BD type, clinical characteristics (family history, suicidal attempts, duration of illness, duration of treatment), type of treatment and gender in relation to sensory sensitivity traits. The highly sensitive person scale (HSPS) including 27 items and distinguishing three parameters: EOE, LST, and AES were used. To assess quality of lithium treatment, the Alda scale was implemented.

Lithium-treated patients obtained significantly lower scores on HSPS total score (4.27 vs. 4.98, p = 0.009) and EOE (4.05 vs. 5.23, p = 0.002), compared to patients treated with other mood stabilizers. AES and LST remained on similar level in both groups (however, the results are limited by insufficient statistical power). Also, the negative correlation between LST score and Alda scale score was obtained (r = -0.484; p = 0.031). There was no difference according to clinical characteristics between BD I and BD II, as well as between males and females.

Longitudinal treatment with lithium could reduce overall SPS traits, particularly "EOE". However, it is possible that low intensity of these traits is a factor in good response to lithium. Also, lithium treatment may not reduce aesthetic sensitivity, parameter related to creativity. "Low sensory threshold" can be considered as negative predictor of lithium treatment outcome.