Sleep has a central role in the regulation and processing of emotion, which may help explain the two-way relationship between insomnia and mental health.4

Poor sleep quality is associated with a higher level of negative emotions and lower levels of positive emotions, while insomnia - particularly early waking insomnia - can be a clinical marker for depression. Chronic insomnia also increases the risk of having a first episode of depression, or a relapse. Conversely, sleep disturbance usually decreases as depressive symptoms improve.4,5,7

Around half of all people with diagnosed insomnia have a co-morbid mental health problem or psychiatric disorder. The online study above indicated the possibility of anxiety in 63 per cent of people with insomnia and depression in 39 per cent of cases.

Data also indicate that insomnia is reported in 60-90 per cent of people with major depression, while around 60 per cent of people with bipolar disorder experience insomnia during depressive episodes.3,5,7