Thyroid Disease Linked With Higher Rates of Manic Relapse In Bipolar Disorder

A prospective study published in Bipolar Disorders found a connection between thyroid disease and manic relapse in bipolar disorder (BD).¹

BD affects an estimated 2.4% of the general population and is associated with high rates of relapse.² A recent meta-analysis, for example, showed that 70% to 80% of patients with BD-I and BD-II experienced at least 1 mood episode during a 4-year follow-up period.³ Such findings underscore the importance of identifying factors that may predict long-term outcomes in this patient population.

In addition to disease-related and psychosocial factors, comorbidities such as hypertension, thyroid disease, and migraine headaches are prevalent in BD, as are psychiatric comorbidities such as anxiety disorders and substance disorders.^4-6 Research regarding the impact of these physical and psychiatric comorbidities on outcomes in BD are limited, although some findings suggest that they negatively affect disease course.

Researchers from several international universities explored these variables in a 4-year naturalistic observational study of patients with BD-I (n=161) and II (n=123) and at least 1 hospital admission. The results show that 54.9% of patients had at least 1 physical comorbidity, and 23.2% had at least 1 psychiatric comorbidity. The prevalence rates of various comorbidities were: metabolic (22.0%); cardiovascular (18.8%); thyroid (18.8); neurological (7.6%); neurotic, stress-related, and somatoform disorders (15.5%); personality disorders (12.0%); and nicotine dependence (52.9%).

No effect on relapse risk was observed for any of these comorbidities except for thyroid disease, which was linked with an increased risk of manic relapse in BD-I (hazard ratio [HR], 2.7; P =.003) even when controlling for the presence of medications or alcohol use disorders.

The relapse risk was especially high among patients with hypothyroidism (HR, 3.7; P <.001). In these patients, there was also an association between increased risk of relapse and increased baseline blood levels of thyroid-stimulating hormone (bTSH; HR=1.07 per milli-international units per liter; P =.011). No effect was found for blood levels of free triiodothyronine (fT₃) or free thyroxine (fT₄).

Taken together, these results highlight the elevated rates of various comorbidities in patients with BD and suggest that thyroid disease should be considered a risk factor for manic relapse. in addition, bTSH may warrant further investigation as a potential treatment target. 

References

1. Amann BL, Radua J, Wunsch C, König B, Simhandl C. Psychiatric and physical comorbidities and their impact on the course of bipolar disorder: A prospective, naturalistic 4-year follow-up study [published online May 22, 2017]. Bipolar Disord. doi:10.1111/bdi.12495
2. Merikangas KR, Jin R, He JP, et al. Prevalence and correlates of bipolar spectrum disorder in the world mental health survey initiative. Arch Gen Psychiatry. 2011;68(3):241-251. doi:10.1001/archgenpsychiatry.2011.12
3. Rosa AR, Magalhães PV, Czepielewski L, et al. Clinical staging in bipolar disorder: focus on cognition and functioning. J Clin Psychiatry. 2014;75(5):E450-E456.  doi:10.4088/JCP.13m08625
4. Forty L, Ulanova A, Jones L, et al. Comorbid medical illness in bipolar disorder. Br J Psychiatry. 2015;205(6):465-472. doi:10.1192/bjp.bp.114.152249
5. Nabavi B, Mitchell AJ, Nutt D. A lifetime prevalence of comorbidity between bipolar affective disorder and anxiety disorders: a meta-analysis of 52 interview-based studies of psychiatric population. EBioMedicine. 2015;2(10):1405-1409. doi:10.1016/j.ebiom.2015.09.006
6. Di Florio A, Craddock N, van den Bree M. Alcohol misuse in bipolar disorder. A systematic review and meta-analysis of comorbidity rates.Eur Psychiatry. 2014;29(3):117-124. doi:10.1016/j.eurpsy.2013.07.004