Sleep and Mental Health: How Treating Insomnia Helps with Depression and Anxiety

When you can’t sleep, your mind doesn’t rest. It spins. Worry piles on worry. The next day, you’re exhausted, irritable, and stuck in a loop that feels impossible to break. If you’re dealing with depression or anxiety, poor sleep isn’t just a side effect-it’s fuel. And treating insomnia isn’t about getting more hours in bed. It’s about rewiring the habits and thoughts that keep you awake-and keep your mood sinking.

Why Insomnia Isn’t Just a Symptom

For years, doctors treated insomnia as a side effect of depression or anxiety. If you were sad or anxious, you probably couldn’t sleep. So they focused on fixing the mood first. But research now shows the opposite is just as true: if you have chronic insomnia, you’re far more likely to develop depression or anxiety-even if you didn’t have them before.

A 2025 study in Frontiers in Psychiatry found that people with long-term insomnia are 40 times more likely to develop severe depression than those who sleep well. That’s not correlation. That’s causation. Your brain gets stuck in a cycle: stress keeps you awake, lack of sleep makes you more sensitive to stress, and your nervous system stays on high alert. Cortisol, the stress hormone, stays elevated. Your body never switches off. Over time, this rewires how your brain handles emotions.

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) recognized this shift in 2013. Insomnia is now listed as its own diagnosis-not just a symptom. That change matters because it means treating sleep isn’t optional. It’s part of the core treatment.

CBT-I: The Only Treatment That Works Long-Term

There are pills for insomnia-zolpidem, zaleplon, eszopiclone. They help you fall asleep faster. But they don’t fix the problem. Once you stop taking them, the insomnia comes back. And they don’t touch the underlying depression or anxiety.

What does work? Cognitive Behavioral Therapy for Insomnia (CBT-I). It’s not a medication. It’s a structured, evidence-based program that targets the thoughts and behaviors keeping you awake. And it’s backed by over 180 studies.

A 2023 review in Sleep journal analyzed 186 studies. The results were clear: people who completed CBT-I had significantly lower rates of developing major depression. In fact, those who fully recovered from their insomnia cut their risk of depression by more than 80% compared to those who still struggled with sleep.

CBT-I isn’t one trick. It’s five tools working together:

1. Stimulus Control-Your bed is only for sleep and sex. No scrolling, no working, no lying there worrying. If you’re not asleep in 20 minutes, get up. Go sit in another room until you feel sleepy. This rebuilds the mental link between bed and sleep.
2. Sleep Restriction-You’re spending 8 hours in bed but only sleeping 5. Instead of lying there frustrated, you limit your time in bed to match your actual sleep. So if you’re only sleeping 5 hours, you’re only allowed in bed for 5 hours. Sounds harsh? It is-at first. But over time, your body learns to sleep more efficiently. Sleep pressure builds, and you fall asleep faster.
3. Relaxation Training-Anxiety doesn’t turn off when the lights go out. Techniques like diaphragmatic breathing and progressive muscle relaxation calm your nervous system. You’re not trying to force sleep-you’re letting go of the fight.
4. Cognitive Therapy-You think, “If I don’t sleep tonight, I’ll be useless tomorrow.” Or, “I’ll never get a good night’s sleep again.” These thoughts keep your brain alert. CBT-I helps you challenge them. Are they true? Are they helpful? What’s the evidence?
5. Sleep Hygiene-Not the fluffy advice you see online. Real sleep hygiene means no caffeine after 2 p.m., no screens an hour before bed, and keeping your room cool and dark. It’s basic, but most people skip it.

Most CBT-I programs run 6 to 8 weeks. You track your sleep in a diary. You get feedback. You adjust. It’s not magic. But it works.

Why Digital CBT-I Is Changing Everything

Finding a trained CBT-I therapist can be hard. In the U.S., fewer than 5% of psychologists are certified in it. Insurance often won’t cover it. That’s why digital platforms like Sleepio and SHUTi are making a difference.

These apps deliver the same CBT-I protocol-step by step, video by video, exercise by exercise. A 2025 study in Nature Scientific Reports found that people using digital CBT-I had a 57% lower chance of developing moderate-to-severe depression than those who just read sleep tips.

Sleepio, used by over 150,000 people, reports that 76% of users see a clinically meaningful drop in insomnia severity. That means they go from struggling every night to sleeping well most nights. And the benefits stick. Unlike pills, CBT-I doesn’t lose its effect after a few months. It teaches skills you keep for life.

Even better-digital CBT-I works just as well for people with depression and anxiety as it does for those without. A 2024 study in JAMA Psychiatry found that combining CBT-I with the antidepressant sertraline led to 40% higher remission rates than the drug alone. Sleep treatment didn’t just help sleep. It helped the depression lift faster.

What Doesn’t Work (And Why)

You’ll hear a lot of advice: melatonin, chamomile tea, weighted blankets, white noise machines. Some of these might help a little. But none of them fix the core problem.

Medications like zolpidem might help you fall asleep the first night. But they don’t change your brain’s sleep habits. They don’t reduce anxiety. They don’t prevent depression. And they come with risks-dizziness, memory issues, dependence. A 2025 study showed that while both CBT-I and zolpidem improved sleep and mood short-term, only CBT-I prevented relapse after treatment ended.

Even “sleep hygiene” advice-like avoiding caffeine or watching TV in bed-is often misunderstood. People think if they just stop drinking coffee after 4 p.m., they’ll sleep better. But if you’re lying in bed for 8 hours thinking, “I have to sleep,” no amount of tea will help. That’s why CBT-I works where other methods fail. It targets the root, not the surface.

The Real Barrier: Access

The science is clear. CBT-I is the gold standard. So why aren’t more people getting it?

Before the pandemic, 8-10% of adults had insomnia. By 2021, that jumped to 18-20%. And nearly one in three people reported clinical insomnia symptoms. Demand exploded. But supply didn’t.

Insurance companies often won’t cover CBT-I unless it’s delivered by a licensed therapist-and even then, reimbursement is low. Many therapists don’t have the training. And while digital options are growing, most people don’t know they exist.

Some health systems are starting to change. Kaiser Permanente began screening all depression patients for insomnia in 2022. Those who got CBT-I had a 22% lower chance of relapsing into depression. That’s not just better sleep. That’s fewer hospital visits, fewer missed workdays, fewer crises.

One study found that for every dollar spent on CBT-I, the healthcare system saved $2.50 to $3.50 in reduced doctor visits, medications, and disability claims. That’s a return most treatments can’t match.

What to Do If You’re Struggling

If you’ve been stuck with insomnia for months-or years-and you’re also feeling down or anxious, here’s what to try:

• Start a sleep diary. Write down when you get in bed, when you fall asleep, when you wake up, and how you feel in the morning. This isn’t just for your doctor-it helps you see patterns.
• Try a digital CBT-I program. Sleepio, SHUTi, and CBT-I Coach are all clinically validated and available on phones or tablets. Many offer free trials.
• Don’t wait for your mood to improve before fixing your sleep. Start with sleep. The mood often follows.
• If you’re on antidepressants, talk to your doctor about adding CBT-I. The combination is stronger than either alone.
• If you’re in the UK, ask your GP about the NHS’s digital CBT-I referral program. It’s free and available to anyone with a prescription.

It’s not easy. The first week of sleep restriction feels brutal. You’ll be tired. You’ll doubt it’s working. But if you stick with it, your body will adapt. You’ll start falling asleep faster. Waking up less. And the constant worry that used to fill your nights? It begins to fade.

Sleep isn’t the enemy. The fear of not sleeping is. And CBT-I helps you let go of that fear-one night at a time.

How Long Until You See Results?

Most people start noticing changes in 2 to 3 weeks. By week 4, many report fewer nighttime awakenings. By week 6, sleep efficiency often jumps from 60% to 85% or higher. And the mood improvements? They follow close behind. You won’t wake up “cured.” But you’ll wake up less exhausted. Less anxious. More in control.

It’s not overnight. But it’s lasting.