Sleep and mental health: depression, anxiety and mood

Which comes first, poor sleep or poor mental health?

Both. Almost every mental health condition disturbs sleep, and insomnia is one of the core symptoms of depression. But the link also runs the other way.

A review of 21 long-term studies found that people with insomnia but no depression at the start were roughly twice as likely to develop depression later (odds ratio about 2.1 to 2.6, depending on the method) as people who slept well. A UK study in North Staffordshire found a similar pattern: among people who slept well at the start, new insomnia a year later was linked with anxiety, depression and pain.

Lab studies show the short-term effect directly. When healthy young adults were limited to about 5 hours a night for a week, their ratings of tension, confusion, fatigue and overall mood disturbance rose day by day.

What did the OASIS trial show?

The strongest evidence that better sleep improves mental health comes from the OASIS trial, run by the University of Oxford at 26 UK universities. It randomly assigned 3,755 students with insomnia to an online CBT for insomnia course (Sleepio) or usual care.

After 10 weeks, compared with usual care, the CBT group had:

• much less insomnia (a large effect),
• fewer paranoid thoughts and hallucinatory experiences (small effects, the main targets of the study),
• less depression and anxiety, and better wellbeing.

Analysis suggested that the improvement in sleep explained a large part of the improvement in mental health. Because people were randomly assigned, this is good evidence that treating insomnia can improve mental health. The trial was in students, and the effects on mental health were small to moderate, which is why we grade the overall claim moderate rather than strong.

NICE now recommends Sleepio for people with insomnia in the NHS. See CBT for insomnia.

What can help?

• Treat insomnia directly if it has lasted months, rather than waiting for it to resolve with mood. CBT for insomnia works for people with depression and anxiety too.
• Keep a regular wake time, even after bad nights. Lying in to catch up can make both sleep and low mood worse.
• Go easy on alcohol, which many people use to wind down but which fragments sleep and worsens low mood.
• Talk to your GP if low mood, anxiety or poor sleep is affecting your daily life. Some antidepressants affect sleep, for better or worse, so mention your sleep when discussing treatment.

If you are in crisis or having thoughts of harming yourself, call NHS 111, contact your GP, or call Samaritans free on 116 123, any time.