Sleep loss can trigger relapse, particularly in the form of mania, in people with a diagnosis of bipolar disorder, finds a study by Cardiff University.

The new research, led by Cardiff University PhD student Katie Lewis, from the National Centre for Mental Health (NCMH), suggests that one in four individuals with bipolar disorder may be at risk of an episode of high mood following sleep loss.

Understanding what factors influence the relationship between sleep and mood episodes could help predict which individuals are most likely to relapse following periods of sleep deprivation, for example, because of long-haul travel or shift work. It could also inform self-management techniques such as e-monitoring.

This is the largest study to date reporting on the prevalence of sleep loss as a trigger in individuals with bipolar disorder and the first study to examine sleep loss as a trigger of both manic and depressive episodes in a large sample of individuals with bipolar disorder.

The large sample size made it possible for the team to examine whether bipolar subtype (type 1 or type 2), as well as gender, could affect people’s vulnerability to sleep loss. Type 1 and type 2 bipolar subtypes can both represent serious mental health conditions, however the main difference between type 1 and type 2 bipolar disorder is that people with type 1 tend to have more severe episodes of high mood, possibly requiring hospitalisation.

Katie Lewis from Cardiff University, who led the research, explained: “We found that 20% of people with bipolar disorder reported that sleep loss had triggered episodes of high mood, whereas 12% reported that sleep loss had triggered episodes of low mood.

“A tendency for sleep loss to trigger episodes of high mood was more likely among women and people with type 1 bipolar disorder.

“This finding was the same when controlling for things like the number of episodes experienced, age and illness severity. In contrast, the tendency for sleep loss to trigger depression appeared to be the same across bipolar subtypes and genders.”

In the study, Katie and her colleagues interviewed 3,140 individuals, drawn as a sample from the Bipolar Disorder Research Network. People were recruited from across the UK, through NHS community mental health teams and patient support organisations such as Bipolar UK.

It is unclear why some individuals become depressed following sleep deprivation and others become manic. It is possible that other triggers associated with relapse in bipolar disorder, such as stressful or exciting life events, medication use or interpersonal conflict, may coincide with the sleep loss that people experience.

Katie concluded: “Future research could potentially look at the role genes play in determining which people are particularly vulnerable to sleep loss triggering episodes of illness.”

The study titled, ‘Sleep loss as a trigger of mood episodes in bipolar disorder: individual differences based on diagnostic subtype and gender,’ was published in the British Journal of Psychiatry.