Explainer: What's the link between insomnia and mental illness?

Poor sleep can make us feel down, worried and stressed. So it's no surprise that how well we sleep has a direct impact on our physical and mental health. Sleep problems such as insomnia are a common symptom of many mental illnesses, including anxiety, depression, schizophrenia, bipolar disorder and attention deficit hyperactivity disorder (ADHD). The relationship between insomnia and mental illness is bidirectional: about 50% of adults with insomnia have a mental health problem, while up to 90% of adults with depression experience sleep problems. Sleep problems can also create a loop, slowing recovery from mental illness. People with depression who continue to experience insomnia, for instance, are less likely to respond to treatment for depression. They are also at greater risk of relapse than those without sleeping problems.