Effectiveness of medical treatment for bipolar disorder regarding suicide, self-harm and psychiatric hospital admission: between- and within-individual study on Danish national data

Background Mood stabilisers are the main treatment for bipolar disorder. However, it is uncertain which drugs have the best outcomes. Aims To investigate whether rates of suicide, self-harm and psychiatric hospital admission in individuals with bipolar disorder differ between mood stabilisers. Method A cohort design was applied to people aged ≥15 years who were diagnosed with bipolar disorder and living in Denmark during 1995–2016. Treatment with lithium, valproate, other mood stabilisers and antipsychotics were compared in between- and within-individual analyses, and adjusted for sociodemographic characteristics and previous self-harm. Results A total of 33 337 individuals with bipolar disorder were included (266 900 person-years). When compared with individuals not receiving treatment, those receiving lithium had a lower rate of suicide (hazard ratio 0.40, 95% CI 0.31–0.51). When comparing treatment and non-treatment periods in the same individuals, lower rates of self-harm were found for lithium (hazard ratio 0.74, 95% CI 0.61–0.91). Lower rates of psychiatric hospital admission were found for all drug categories compared with non-treatment periods in within-individual analyses (P<0.001). The low rates of self-harm and hospital admission for lithium in within-individual analyses were supported by results of between-individual analyses. Conclusions Lithium was associated with lower rates of suicide, self-harm and psychiatric hospital readmission in all analyses. With respect to suicide, lithium was superior to no treatment. Although confounding by indication cannot be excluded, lithium seems to have better outcomes in the treatment of bipolar disorder than other mood stabilisers.