The connection between sleeping long durations or suffering from insomnia differs between the different bipolar disorder (BD) subtypes, according to new research.

A team led by Katie J. S. Lewis, PhD, Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Institute of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, conducted a case-control study in the UK and Sweden involving 4672 patients with bipolar disorder, as well as 5714 control participants to test whether genetic liability to insomnia, hypersomnia, and chronotype differentiate subtypes of bipolar disorder.

The investigators found that patients with bipolar disorder I had significantly greater genetic liability to sleep longer durations, while patients with bipolar disorder II had significantly greater genetic liability to insomnia.

The team then replicated the results in an independent sample and found that individuals with bipolar subtypes did not differ in genetic liability to morning or evening chronotype.