Sleep and depression or anxiety: a two-way relationship

Sleeping poorly and feeling down or anxious often go hand in hand — but which is the cause and which the effect? The surprising answer is: both at the same time. The relationship between sleep and depression or anxiety runs in two directions. Insomnia is not only a consequence of mental health problems, but also a factor that can fuel them and keep them going. And that's where the good news lies: treating your sleep can also help your mood and anxiety. This article explains the two-way relationship and what it means for how to approach it.

Sleep and mood: a two-way relationship

For a long time, insomnia was seen mainly as a symptom of depression and anxiety — something that would disappear on its own once the underlying disorder had been treated. That picture is outdated. Research over the past decades shows that the link works in both directions: mental health problems disrupt your sleep, but disrupted sleep in turn feeds low mood, anxiety and irritability ^[1].

That makes insomnia more than a side effect. It's a point of intervention in its own right — a lever you can pull to break the vicious cycle.

Insomnia as a risk factor

The strongest evidence comes from long-term (longitudinal) studies that follow people over many years. An influential meta-analysis of that type of research found that people with insomnia who were not depressed at the time had roughly a twice-as-high chance of later developing depression than people who slept well ^[1].

It doesn't stop at depression. A broader systematic review showed that insomnia also predicts the onset of anxiety disorders and contributes to the persistence of depression. The authors suggest that insomnia is a kind of transdiagnostic risk factor: a shared driver behind several mental health conditions ^[2].

Insomnia as a symptom

At the same time, poor sleep is one of the most common symptoms of depression and anxiety. With depression it often involves trouble staying asleep and waking too early; with anxiety it mainly involves trouble falling asleep due to a restless, tense mind. The NHG guideline and Thuisarts.nl therefore stress that, for persistent sleep complaints, the GP also checks whether there is low mood, anxiety or tension that needs to be treated alongside ^[6][7].

The problem: if only the depression or anxiety is treated, the insomnia often lingers. And it is precisely that lingering insomnia that increases the chance of relapse. That's an important reason not to treat sleep as a side issue.

Treating sleep often improves mood too

Here comes the encouraging part. If you tackle sleep directly with CBT-i (cognitive behavioral therapy for insomnia), not only does sleep improve, but often mood and anxiety as well.

A large randomized study of over 3,700 students (the OASIS trial) showed that digital CBT-i not only reduced insomnia, but also reduced paranoia, hallucinations, anxiety and low mood — and that the improvement in sleep partly explained those effects ^[3]. A meta-analysis of digital CBT-i reached a similar conclusion: alongside better sleep, a decrease in depressive and anxiety symptoms was seen ^[4].

Treat side by side, not one after the other

The old idea "treat the depression first and the sleep will follow" is therefore often wrong. Because sleep and mood influence each other back and forth, they are increasingly treated side by side: the depression or anxiety according to the usual approach, and the insomnia with CBT-i. The European insomnia guideline recommends CBT-i as the first-line treatment for insomnia, even when other complaints are involved ^[5].

When to see your GP?

See your GP if poor sleep goes together for longer than a few weeks with low mood, anxiety, irritability or loss of pleasure, or if your symptoms interfere with your daily functioning ^[7]. Your GP or practice nurse (POH-GGZ) can examine you, guide you or refer you — for example to CBT-i, psychological treatment, or both.

Sleep and mood are inextricably linked, in both directions. That may sound like a trap, but it is above all an opportunity: by taking your sleep seriously and treating it purposefully, you often help your mood and anxiety along too. If you keep sleeping poorly or feeling down, don't wait it out — raise it with your GP and ask about CBT-i alongside care for your mental health complaints.