Taking certain antidepressants for depression is linked to a greater risk of subsequent mania and a new diagnosis of bipolar disorder, according to a new study published in the online journal BMJ Open.
The strongest link was found with serotonin reuptake inhibitors (SSRIs) and the dual action antidepressant venlafaxine, according to the findings. These drugs were associated with a 34-35 percent increased risk of being later diagnosed with bipolar disorder and/or mania.
For the study, researchers analyzed the medical records of more than 21,000 adults who had been treated for major (unipolar) depression between 2006 and 2013 at a large provider of inpatient and community mental healthcare in London. They also looked at subsequent diagnoses of bipolar disorder or mania following an original diagnosis of major depression.
The overall yearly risk of a new diagnosis of mania and bipolar disorder between 2006 and 2013 was 1.1 percent. Prior treatment with certain antidepressants was linked to a greater risk of a subsequent diagnosis of bipolar disorder and/or mania, the yearly risk of which ranged from 1.3 percent to 1.9 percent.
The risk was particularly high after patients had received treatment with SSRIs or venlafaxine. These drugs were associated with a 34-35 percent increased risk of being diagnosed with bipolar disorder and/or mania. The findings remained strong even after taking account of potentially influential factors.
Since this is an observational study, no firm conclusions can be drawn about cause and effect. The researchers suggest that the findings may be explained by latent bipolar disorder rather than any effects of drug treatment.
“However, regardless of underlying diagnosis or aetiology the association of antidepressant therapy with mania demonstrated in the present and previous studies highlights the importance of considering whether an individual who presents with depression could be at high risk of future episodes of mania,” say the researchers.
Risk factors include a family history of bipolar disorder, a depressive episode with psychotic symptoms, young age at first diagnosis of depression, and depression that is unresponsive to treatment.
“Our findings also highlight an ongoing need to develop better ways to predict future risk of mania in people with no prior history of bipolar disorder who present with an episode of depression,” they write.
The researchers also note that the absolute risk of developing bipolar disorder is still low and that antidepressants are typically safe and effective treatments for depression and anxiety. They advise that patients not stop their treatments suddenly as this could result in withdrawal symptoms.