What causes insomnia?

Published On: November 6, 2023
Published By: London Sleep Coach

Struggling to work out why you can’t sleep? Various factors can cause insomnia, and while everyone’s experience is unique, there are some common culprits. Discover below some of the main reasons why insomnia happens, helping you to better understand your issue with sleep and find a way forward.

Bad sleep doesn’t always mean insomnia

Firstly if you’re only having trouble sleeping every once in a while, don’t worry about it. Most people sleep badly now and again, sometimes for no obvious reason, but especially when life gets stressful and challenging. This is normal and doesn’t necessarily mean insomnia is the issue. Even the best sleepers have bad nights when under stress. But if bad night after bad night seems to keep on happening, this could indicate a bigger problem.

Since you’re reading this article, I suspect you’re currently somewhat bothered by your sleep, or lack of it. Bear in mind that ‘Insomnia’ is a descriptive term and not a definitive diagnosis. It is not a disease you are stuck with, however bad it might feel or despite how long you’ve been experiencing it. So try not to get too bogged down deciphering whether or not you are an ‘insomniac’ by definition or not. If you’re unhappy with your sleep, then that’s what’s important, you not being happy about it. As is usually the case, labels are often unhelpful and don’t tell the full story.

How do you know if you’re suffering from insomnia?

You may think it’s obvious in that you just can’t sleep, but this is incorrect and misleading. Firstly no insomniac never sleeps, despite what they might think, someone will always sleep eventually. Our biological sleep drive just gets too big to stop anyone from sleeping after being awake for long enough. Secondly most insomniacs do actually sleep each night. They might not get much sleep, but it’s rare to go through a whole night without any sleep whatsoever.

The exact symptoms of insomnia are varied but typically include regularly suffering from one or more of the following over an extended period of time:

  • Getting less than six hours of sleep at night.
  • Feeling sleepy and or especially tired during the day.
  • Struggling to fall asleep when going to bed.
  • Waking up too early and not being able to get back to sleep.
  • Waking up often during the night and struggling to fall asleep again.
  • Feeling anxious, worried and stressed about sleep.
  • Sleep issues negatively affecting other areas of life, such as relationships and work.

Insomnia isn’t always the same for everyone and one way it’s categorised is by how long someone’s been suffering from it, either being acutely or chronically:

Acute Insomnia:

This is short-term insomnia that lasts from a few days to a few weeks. It’s usually caused by something stressful happening in life, such as exams, break ups, work stress, health scares, pregnancy or grieving. It can also be caused by jet lag, shift work, some medications and being ill. This type of insomnia often goes away on its own when the difficult period passes over.

Chronic Insomnia:

This is the long-term kind and is where routinely sleeping badly has consistently lasted for more than three months. It might be because of underlying health problems (mental or physical), lifestyle factors and chronically high stress levels. More often though, chronic insomnia is a sleep-anxiety related issue, whereby anxiety, worry and stress about sleep consistently disrupt it. This often leads to other problematic behaviours and habitual patterns of thinking that further disrupt sleep.

At the surface level the main distinction between these two categories of insomnia is time, i.e. how long has someone been sleeping badly for. However, another key difference between the two is someone’s perception of the problem and how much they see sleep as being a problem negatively affecting their life.

Someone with ‘chronic insomnia’ is fully aware they’ve got an issue with sleep, and for them sleep becomes a problem in and of itself. Their thoughts and feelings around sleep lead to constant hyperarousal (feeling alert), anxiety and worry at night, routinely making sleep difficult. Sleep, or lack of it, often becomes a source of fear for these individuals. Not that they’re scared of sleeping, but rather they regularly fear they won’t sleep and how this will affect them.

Whereas someone with ‘acute insomnia’ likely sees their difficulty sleeping as a temporary symptom and not their main issue. They put their difficulty sleeping down to a particularly stressful or challenging thing that has emerged in their lives. Consequently they’ll likely think that when this stressor in their life resolves itself, so will the sleep problem, as is often the case.

The good news is: sleep problems can always get better. You don’t have to suffer and can get help with the problem. Sleep is important, and you deserve to rest well. Acceptance & Commitment Therapy for insomnia might just be the solution you need.

Insomnia as a Primary or Secondary symptom

The reasons why insomnia happens are complex and it can often be hard to clarify its precise causes. Broadly speaking there are two main categories that an individual will fall under for the cause of their insomnia, being either primary or secondary insomnia, which are explained below:

Primary Insomnia

This is when you can’t sleep, and there’s no obvious reason for it. There’s no underlying medical condition affecting your sleep or other obvious factors. In these instances insomnia can seem to be happening for no apparent reason.

It’s usually got a psychological part, whereby racing thoughts keep you awake, often being described as feeling like your mind won’t turn off and let you rest. These negative thought patterns also tend to lead to other problematic behaviours. It’s also got a physiological part, in which you experience uncomfortable feelings such as anxiety, panic, worry and hyperarousal at night keeping you awake too.

In this category people typically worry about not sleeping and what this lack of sleep might do to them. This then makes them more stressed and anxious, keeping them awake even more. Hence insomnia can quickly become a vicious cycle. Often it’s this worry and anxiety around sleep that affects insomniacs’ well-being the most, even more than the missed sleep itself.

It can be likened to feeling as though there’s a radio in your head that’s constantly spouting anxious, worrisome gloomy thoughts about sleep. These thoughts typically bring difficult feelings with them and can seem to go on and on, happening during the day as well as at night.

Primary insomnia can have a devastating effect on people’s quality of life and should always be taken seriously. Unfortunately it’s something people often put up with for a long time and may not actively seek help for either. The reason typically being that they’ve given up hope anything can solve their issue with sleep.

Secondary Insomnia

This kind of insomnia is different. It happens as a result of another health problem disrupting your sleep, causing you to not get enough of it. It might be a sleep disorder like restless legs syndrome, shift work disorder or sleep apnoea, or undergoing intensive medical treatment, such as for cancer, or suffering from chronic pain conditions. Even some medications can negatively affect sleep and cause insomnia. Substance abuse of alcohol and drugs can be another cause.

If you have insomnia because of these issues, medical treatment for the underlying problem typically resolves the insomnia. However, insomnia can also need individual treatment, as it can sometimes be improved despite the other health problem not yet being fully resolved, and occasionally the insomnia symptoms persist even after the original health issue has dissipated.

Insomnia and Mental Health

Insomnia can play a massive part in mental health conditions, such as in depression and anxiety based ones. However insomnia and mental health is a complex relationship. Suffering from long term insomnia can be a cause of mental health problems and equally initial mental health problems can also cause both short and long term insomnia. Think of it like the ‘chicken and egg’ puzzle – It’s not often clear whether the sleep problem or mental health problem happened first.

Importantly insomnia symptoms can get better when treated individually despite ongoing depression and anxiety issues. It’s also possible that with better sleep the depression and anxiety symptoms can improve too.

The relationship between stress and insomnia

Stress is something we all feel, and it seems like 21st century life today has only made our stress levels much worse. High stress levels certainly don’t help sleep and can be a contributing factor towards both triggering and maintaining insomnia symptoms. When we’re more stressed we’re more alert, tense and constantly problem solving in our heads, making sleep more difficult. We may even be more anxious and worried as a result of being highly stressed, which further disrupts sleep.

But it’s not that black and white. You don’t have to completely get rid of stress to sleep well at night. You can still sleep okay despite being stressed in life.

I am sure you know or can think of someone who is always under a lot of pressure, living an intensely stressful life, but still manages to sleep fine. That’s not to make you jealous, but to show you that it’s completely possible to have stress in your life and still get a good night’s sleep.

If you’re doubting this, try to remember a time when you yourself were previously experiencing a lot of stress but still slept well. Most people suffering with insomnia can name plenty of occasions when they’ve previously slept okay, despite being under stress. Even if you can’t recall such a moment, don’t worry, the key takeaway is you can always learn to sleep better, even with stress in your life.

Think about those times when everything seems to be going wrong, such as when you’re overwhelmed at work or dealing with something difficult in your personal life. In these moments just because you’re stressed it doesn’t mean you should have to lose sleep over it.

Sleeping well despite stress is where ACT comes in. ACT doesn’t try to get rid of your stress but helps you to sleep well even when stressed. Lots of things that are really important to us in life are stressful. That’s why it’s important that we can learn to sleep okay despite stress, empowering us, as opposed to us shying away from stress.

ACT doesn’t tell you to change your life to reduce stress, especially if that stress comes from something you value like being a new parent, working hard on a project you care about, or managing an important relationship. Instead it helps you to sleep in whatever situation you find yourself in.

Of course it’s normal for your sleep to be a bit off during particularly tough times, and that’s okay. This doesn’t mean, though, that sleep has to be really bad or become a problem in your life. Challenging times will happen in life and knowing how to react in these moments towards ourselves and our sleep can make all the difference.

In the long run, you might decide to make some changes in your life to reduce your stress levels, and that’s great. Though sometimes we don’t have much control over what stresses us, and that’s where ACT can really help. It helps you to sleep well despite what’s happening in your life, even when things get hard.

Lifestyle factors and insomnia

Insomnia can be influenced by several lifestyle factors, so it’s worth assessing if any of these apply to you. We hear lots about the importance of keeping good habits in order to sleep better, but bear in mind that lots of this advice is exaggerated. Let’s break down some common lifestyle factors that might be keeping you up at night, and some things you might not need to worry about.


If you’re drinking energy drinks or loads of coffee or tea late in the day, it might be keeping you awake somewhat. But here’s the twist: if you’re only having a few cups, it probably isn’t the caffeine that’s the problem, but more likely your worry about how the caffeine could affect your sleep. Think of all those people you know who drink way too much caffeine and still sleep. So, if you enjoy your coffee, keep drinking it, just keep an eye on how much you have and when. Ideally stick to just a few cups earlier in the day.

Exercise and sunlight

Sitting inside all day living a sedentary life isn’t great for sleep and getting some exercise and sunlight can help. But don’t stress about these. You don’t need to exercise everyday or be outside all day getting lots of sunlight to sleep well. In fact, worrying too much about exercising and getting the right amount of sunlight for your sleep will likely make things worse.


Drinking a lot, especially right before bed, can be very detrimental to sleep. Some people might think a little alcohol will help them fall asleep, but it’s a terrible sleep aid for lots of reasons. Chronic insomniacs can also sometimes turn to alcohol for relief to help them sleep, which may lead to a vicious cycle of insomnia and alcohol dependency. Therefore the bottom line is alcohol is never good for sleep.

But at the same time don’t worry about an occasional few social drinks. Firstly it won’t affect your sleep too badly; it probably hasn’t in the past. Secondly if this is something you enjoy and is important to you in life, then do what you value.

Late nights

Consistently going to bed too late can deprive you of sleep and disrupt your body clock, which can lead to insomnia symptoms. However, it’s okay to have fun, enjoy life and stay up late every now and again. A late night out with friends and family isn’t going to ruin your sleep. Equally if you’re working late on something you value, that’s important too.

It’s good to prioritise sleep some nights of the week, but we don’t always have to go to bed on time. Life is about much more than getting a great night’s sleep. Sleep shouldn’t be controlling your life, you should be making the most of it.

Shift work

If you work night shifts or irregular hours, it’s likely to disrupt your sleep patterns, making sleep temporarily challenging. In some cases this short term disruption can lead to longer term insomnia symptoms. But there’s no guarantees here and some people’s sleep is less bothered by shift patterns than others. But be aware if you’re following this kind of schedule, it’s still possible to mitigate the disruption to your sleep. Secondly, the importance of shift work in some sectors might justify some temporary disruption to your sleep.

Snoring partners

Sleeping next to a fog horn or someone making annoying breathing sounds can be really difficult. Most people try one of four things to deal with this: they try ear plugs; they put up with it; they try to mentally block it out; or they sleep in another room. Unfortunately none of these options are that great or sustainable.

So if the snoring is untreatable and can’t be stopped (note sometimes snoring is treatable), what do you do? The answer may lie in your reaction to the problem. Many people sleep soundly next to a snoring partner without getting bothered by it. ACT can be really useful at helping people get less bothered and wound up by their partners snoring.

Lastly, please note that insomnia isn’t just about these lifestyle factors and often isn’t at all, as usually it comes from psychological concerns. If you find that you’ve already considered all these aspects and still can’t sleep, don’t go round in circles and don’t hesitate to seek help.

The Three Ps of insomnia

If you’re routinely having trouble with chronic insomnia and find yourself worrying about what’s caused the issue, the Three Ps of insomnia model can help you figure out why it’s happening to you. However, be mindful that simply understanding what’s causing your insomnia doesn’t necessarily solve it; taking steps to address the issue is the key. It’s similar to when we may understand why we’re feeling low, sad or anxious, but this understanding often doesn’t stop or improve the feelings by itself.

Often we get stuck wondering why we can’t sleep. Some fear serious medical reasons, like a hidden brain tumour, but this is usually just our mind fear mongering. Most of the time, there’s nothing physically wrong with someone suffering from insomnia. Usually it’s just a combination of bad habits, worry, stress and getting anxious about sleep that keep the problem happening. The Three Ps model helps to explain the causes of insomnia when it’s this more psychologically rooted issue.

Before looking at the model be aware that the Three Ps is just a model, and like most models it’s useful but doesn’t apply to everyone. The three Ps in the model stand for Predisposing Factors, Precipitating Factors, and Perpetuating Factors. In the model the factors that apply to an individual typically happen in that order, leading to up experiencing chronic insomnia.

Predisposing Factors

These are factors that might make you more prone to initially developing sleep problems in life. Examples of these include having a family history of insomnia, experiencing chronic stress, suffering adverse childhood experiences, being old, or living in poverty. But just because some of these factors may apply to you doesn’t mean you’ll definitely develop insomnia.

Equally, sometimes people develop insomnia without any obvious predisposing factors. Think of these factors like heart disease. Many factors increase your risk of developing the condition, but none of them guarantee you’ll have a heart attack. You can also be mostly healthy and still get heart disease, which also applies to insomnia.

Precipitating Factors

These are specific events or changes that happen to you in life and cause initial disruption to your sleep for a few days or weeks. It may be undergoing a traumatic event, suffering from an illness (mental or physical), money worries, a stressful period at work, undergoing pregnancy, looking after a newborn or having new noisy neighbours.

Many can point to when their sleep troubles first began because of a specific factor. However, these factors do not always lead to long-term insomnia. Sleep problems can often resolve on their own as and when the original stressor dissipates.

Perpetuating Factors

This is when short term sleep troubles turn long-term and become chronic. These factors are the behaviours, habits or thought patterns that creep in and keep the insomnia going, typically after the precipitating factors have subsided. Maybe you start doubting your natural ability to sleep, get anxious about sleep, obsess over getting enough sleep, rely too much on sleeping pills or drink too much coffee or alcohol, all of which exacerbate the insomnia symptoms. These factors can make sleep problems stick around chronically.

Again knowing and understanding all this isn’t enough. You have to actually do something about your insomnia problem. Acceptance and Commitment Therapy is one method that can really help you to get to the root of your problem.

Understanding your expectations of sleep

It’s helpful to be aware that sometimes people think they’re suffering from insomnia, when in actual fact they aren’t. Through no fault of their own they may have overly high expectations for their sleep, which causes problems when their sleep doesn’t match up to them. This then understandably makes some question if they are suffering from insomnia. Therefore knowing a little bit more about what you should realistically expect from your own sleep could take away some stress and worry.

The following are some common things to be aware of:

Sleep changes as we age

As people get older, they may find their sleep patterns changing. This doesn’t mean their sleep is getting worse; it’s just different. Seniors might wake up more often during the night, need the bathroom more and find it harder to sleep in late. They may also need slightly less sleep than younger adults. So, if you’re seventy expecting to sleep like you did at thirty, you’ll likely end up feeling frustrated.

Teenagers often naturally go to bed later and wake up later than most adults. They find it harder to fall asleep earlier in the evening, when other adults go to sleep, and can’t get up as easily early in the morning. This is because their circadian rhythms are inherently shifted to be later than older adults and they also need more sleep per night. These sleep pattern differences are typical for their age.

Not everyone needs the same amount of sleep

You’ve probably heard that eight hours is the magic number, but that’s not true for everyone. Some people might feel great on just six and a half hours of sleep. Like shoe sizes, sleep needs vary from person to person and many people don’t need as much as eight hours. All that matters is that you feel reasonably well rested the next day.

Waking up at night is normal

If you wake up a few times during the night, don’t worry. Our sleep usually follows 90-minute cycles, and it’s not uncommon to briefly wake up at the end of them. Importantly this means you shouldn’t give up on sleep if you find yourself waking up earlier than expected. Instead stay in bed resting and let sleep naturally return to you.

Perfect sleep is a myth

Everyone has nights when they don’t sleep well, especially during stressful or challenging times. Trying too hard to consistently attain great sleep can also be problematic by putting too much pressure and emphasis on it. Accepting that sleep won’t always be perfect is essential, as perfectionism is only likely to heighten levels of anxiety around sleep, making it worse.

You may be sleeping more than you think

Some people think that they’re not sleeping that much when they actually are. People notoriously think it takes them longer to fall asleep than it actually does and typically underestimate how much they’ve slept in a night.

On the far end of the spectrum, this is something called ‘paradoxical insomnia,’ whereby people become convinced they’re not sleeping well and are suffering from insomnia, only to find out in a sleep study that they’re sleeping relatively normally.

Feeling tired doesn’t always mean bad sleep

Feeling sleepy and feeling tired are two different things. If you feel tired, it might not be because of poor sleep. An endless list of many different factors and reasons can make you feel tired. That’s not to say insomnia doesn’t make you feel tired, but this is just something to be aware of. However, if you still feel sleepy late in the morning, that might be one sign that you’re not getting enough good sleep.

In the end, sleep is a personal and sometimes complex part of our lives. It’s quite normal and expected for people to have different sleep patterns and needs. Recognising and accepting these facts can help you stress less and sleep better.

Whilst these are important things to bear in mind, if sleep has become a problem for you, education is not always enough. Often those struggling with insomnia need real help, for example by using ACT.

Struggling with sleep?

I can help you to resolve your difficulty sleeping using Acceptance & Commitment Therapy (ACT).

ACT is an approach that is:

  • Drug and gimmick free
  • Clinically proven and endorsed by NICE
  • A long term solution
  • Tailored to your specific issue
  • Simple and straightforward

Complete my free online course to find out more about how ACT can help.

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