Individuals with bipolar disorder have the lowest risk of rehospitalization if treated with lithium, according to a study from the University of Eastern Finland and Karolinska Institutet published in JAMA Psychiatry. Long-acting injections of antipsychotics were also effective, reducing the risk of rehospitalization by 30% compared with their oral counterparts.

Bipolar disorder is characterized by alternating periods of depression and elevated mood (mania), and is usually treated either with mood-stabilizing or antipsychotic drugs. Lithium is considered to be the most effective mood stabilizer, but only a few studies have been conducted comparing the long-term effects of different drugs in bipolar disorder.

In order to determine which treatment is most effective, researchers at Karolinska Institutet compared the risk of re-admission to hospital in more than 18,000 patients in Finland who had previously been hospitalized for bipolar disorder. Each patient was used as their own control and compared during periods with and without treatment.

Should remain first-line treatment

During an average follow-up time of more than 7 years, lithium treatment was associated with the lowest risk of rehospitalization in mental or physical disease, with a risk reduction of about 30% compared with no treatment at all. Long-acting injections of antipsychotic drugs were also effective. The risk of re-admission was around 30% lower if patients were treated with long-acting injections compared to their receiving the same antipsychotic medication but orally. The most commonly prescribed antipsychotic drug for bipolar disorder, quetiapine (Seroquel), which is given in tablet form, reduced the risk by only 7%.

“The prescription of lithium has decreased steadily in recent years, but our results show that lithium should remain the first line of treatment for patients with bipolar disorder. Long-acting injections might offer a safe, effective option for patients for whom lithium is not suitable”, says Jari Tiihonen, specialist doctor and professor at the University of Eastern Finland and Karolinska Institutet’s Department of Clinical Neuroscience.