# Sudden mood swings: why they happen and when they are something more

> In the morning everything is fine and by mid-afternoon you snap at the smallest thing. Why sudden mood swings happen, what is normal and when it is worth looking more closely.

*https://mypsicotest.com/en/blog/sudden-mood-swings/ · Published: 2026-10-14 · 9 min read · MyPsicoTest team*

In the morning you were in a good mood. At lunchtime, a throwaway comment hit you hard, and by mid-afternoon you can no longer remember why you got so angry. People at home say there is no understanding you, and the worst part is that you do not understand yourself either.

**Sudden mood swings** are very common and nearly always have a simple explanation, but sometimes they are a sign of something that deserves attention. This guide explains what is normal, the causes that usually lie behind them, how to tell them apart by how long each change lasts, when it is worth getting checked and which tests can help you see whether something more is going on.


## What is normal and what is not with mood swings

Mood rises and falls over the day and the week, and that is healthy. Good news lifts you, an argument knocks you off balance and after a while you are back where you started. Usually, the changes are in proportion to what is happening, pass in a reasonable time and do not change your sleep or the way you make decisions.

It is worth paying closer attention when:

- Your reaction is far stronger than the situation called for.
- The changes come without a clear reason or happen almost every day.
- They last days or weeks, not hours.
- They come with changes in your sleep, energy or appetite.
- They are costing you arguments, problems at work or decisions you later regret.
- People close to you say you do not seem like yourself.



![Couple arguing in their kitchen, he with his arms spread wide and she with her back to the camera, one of the effects of sudden mood swings on relationships](https://mypsicotest.com/assets/img/blog-cambios-de-humor-discusion-pareja-1200.webp)



The [NHS](https://www.nhs.uk/mental-health/conditions/bipolar-disorder/) advises seeing a GP if you have extreme changes in your moods that last a long time or affect your everyday life.


## Causes of sudden mood swings

### Not sleeping enough

This is the most underrated cause. A [meta-analysis by Tomaso, Johnson and Nelson](https://pubmed.ncbi.nlm.nih.gov/33367799/) pooled 64 studies on the effects of cutting sleep short or staying up all night. Sleep loss moderately increased negative mood and, above all, dampened good mood, with a large effect on positive mood. A whole night without sleep affected negative mood more than losing a few hours. In other words, when you are short of sleep, good things lift you less and bad things weigh more.

### Stress, alcohol and other substances

A period of heavy pressure shrinks your margin: what you would let go on another day makes you snap. Alcohol, cannabis and stimulants also affect mood, and so do some medicines. If the changes began at the same time as a new treatment, mention it to your doctor.

### Hormones

The NHS explains that most women have premenstrual syndrome at some point, and that its most common symptoms, in the weeks before a period, include mood swings, irritability, low mood or anxiety. A small number of women have a much more intense form, **premenstrual dysphoric disorder**, with anxiety, anger or low mood that hits everyday life hard. Mood swings and low mood are also common during perimenopause and get worse with poor sleep. And an overactive thyroid can cause nervousness, irritability and mood swings; a blood test helps rule it out.

### Depression and anxiety

Depression does not always show as sadness. Among its symptoms, the NHS lists feeling irritable and intolerant of others. In generalised anxiety disorder it is also common to feel restless, irritable and unable to concentrate. In both cases the change in mood does not come and go within a few hours: it is a background that lasts for weeks.

### ADHD

Many adults with ADHD recognise that they get angry quickly, are easily frustrated and go from nought to a hundred. A [meta-analysis by Beheshti and colleagues](https://pubmed.ncbi.nlm.nih.gov/32164655/), with 13 studies and more than 2,500 adults, found much greater emotional dysregulation in adults with ADHD than in adults without it, and the most marked feature was **emotional lability**, rapid shifts from one emotion to another. The more severe the ADHD, the more dysregulation there was. The authors see it as a core part of the condition, not an add-on.

### Borderline personality disorder

In borderline personality disorder, mood swings are intense and very fast. The NHS describes how someone can go from deep despair to feeling reasonably positive a few hours later, in unpredictable ways, and how long-term feelings of emptiness and loneliness are common. The swings are often set off by conflict or by fear of being abandoned.

### Bipolar disorder and cyclothymia

In bipolar disorder, the changes are not a matter of hours. The NHS explains that there are periods of high mood, mania or its milder form, hypomania, and periods of low mood, which usually last a few days or weeks at a time, with stable periods in between. During the highs there is a lot of energy, less need for sleep, racing thoughts, talking fast and a lot, irritability or impulsive spending. The NHS itself acknowledges that diagnosis can take time, because the symptoms are similar to those of other mental health conditions. When the highs and lows are milder but almost constant, it is called cyclothymia, which we explain in [Cyclothymia: what it is, symptoms and how it differs from bipolar disorder](https://mypsicotest.com/en/blog/cyclothymia-symptoms/).


## How long each change lasts: the most useful clue

There is no exact rule, but how long each change lasts, and what comes with it, helps a great deal:

| What the change is like | What usually lies behind it | Which test can guide you |
|---|---|---|
| Lasts minutes or hours, has a reason and passes | A normal reaction, tiredness or stress | Stress Test, if you are going through a period of overload |
| Fast, intense reactions for as long as you can remember, with impulsivity and absent-mindedness | ADHD | ADHD Test |
| Unpredictable changes over hours, with emptiness and fear of abandonment | Borderline personality disorder | No test here: see a professional |
| Weeks of sadness, irritability or loss of interest | Depression | Depression Test |
| Days or weeks "up", with more energy and less sleep, alternating with lows | Bipolar disorder or cyclothymia | Bipolar Disorder Test |
| Repeats every month, in the weeks before a period | Premenstrual syndrome or premenstrual dysphoric disorder | See your GP or gynaecologist |

It is a clue, not a diagnosis: conditions overlap and the same person can have more than one.


## Is there a test for sudden mood swings?

There is no single test for **mood swings**, because they are not a diagnosis but a symptom with many possible causes. The one that explores them most directly is the MyPsicoTest [Bipolar Disorder Test](https://mypsicotest.com/en/bipolar-disorder-test/), which starts with exactly that question: whether your highs and lows are more than mood swings.

It has 16 questions that take about five minutes, and unlike other tests they do not ask about the last few weeks but about your whole life. They fall into three areas:

- **Elation, energy and irritability:** eight questions about spells of several days with more energy, less sleep, rushed speech or impulsive decisions.
- **Depressive episodes:** four questions about periods of at least two weeks of sadness, emptiness or loss of interest.
- **Alternation and impact:** four questions about whether those changes happen together, alternate, are noticed by others and have caused you problems. One of them is this: "Have people close to you (family, partner, friends, colleagues) told you that your changes in mood or energy are abrupt, striking or worrying?"

The score runs from 0 to 64 and comes broken down by area. As the test page itself explains, the most characteristic sign of bipolar disorder is a high score on elation together with a high score on alternation and impact, while a high score only in the depressive area points more towards depression. One tip from the same page: spells of elation are usually remembered as "good times", so if in doubt, think about what the people who know you well would say about those days. The result is calculated in your browser and your answers are not stored.

### Other tests that may help

If you recognise yourself more in lifelong fast reactions, with absent-mindedness and impulsivity, the [ADHD Test](https://mypsicotest.com/en/adhd-test-adults/) can point you in the right direction. If the change in mood is more of a background of sadness or irritability that lasts for weeks, try the [Depression Test](https://mypsicotest.com/en/depression-test/), and if you sleep badly and notice your mood is worse after bad nights, the [Insomnia Test](https://mypsicotest.com/en/insomnia-test/). All the questionnaires, free and anonymous, are in the [psychological tests](https://mypsicotest.com/en/psychological-tests/) catalogue.


## What to do about sudden mood swings

### Keep notes for a few weeks

A simple record tells you more than any memory. Each night, note your mood for the day from 1 to 10, how many hours you slept, whether you drank alcohol, what happened and, if you have periods, which day of your cycle it is. The NHS recommends keeping a symptom diary for at least two menstrual cycles if you suspect premenstrual syndrome, and the same habit works for the other causes: after a few weeks you can see whether the changes depend on sleep, your period, what is happening or nothing in particular.

### Look after what weighs most

Going to bed at regular times, drinking less and slowing down during periods of pressure will not solve everything, but they greatly reduce the swings that come from tiredness and stress.

### When to get help

See a professional if the changes are extreme, if they persist or if they are affecting your work, your relationship or your family. Do it as soon as possible if you have had spells of great energy while sleeping very little and doing things that are not like you, and tell your doctor if an antidepressant has made you elated, sleepless or irritable. And one sign that cannot wait: if thoughts of harming yourself appear, or thoughts that it would be better not to carry on, call the **024 line** in Spain (free, confidential, around the clock), **112**, or your local emergency number.

A good first step is to take the test and bring the result, along with your mood record, to your doctor or a psychologist. At the end of the test you will find our recommendation of a licensed psychologist who works with anxiety, depression and ADHD, also online.

## Frequently asked questions

### Is it normal to have sudden mood swings?

Having ups and downs is normal, especially if you are short of sleep or under pressure. It stops being normal when the changes are out of proportion, happen almost every day, last days or weeks or cause problems at work or in your relationships.

### What can cause sudden mood changes?

The most common causes are lack of sleep, stress, alcohol and other substances, and hormonal changes. Depression, anxiety, ADHD, borderline personality disorder, bipolar disorder or a thyroid problem can also be behind them.

### How do I know if my mood swings are bipolar disorder?

In bipolar disorder the changes do not last hours but days or weeks, and during the highs there is more energy, less need for sleep and behaviour that is not like you. If that sounds familiar, the bipolar disorder test helps you organise what is happening before you discuss it with a professional.

### Does ADHD cause mood swings?

Yes, it is very common. A meta-analysis found much greater emotional dysregulation in adults with ADHD, especially rapid shifts from one emotion to another, and the authors see it as a core part of the condition.

### Can hormones cause mood swings?

Yes. Premenstrual syndrome, perimenopause and an overactive thyroid can all cause them. If they repeat every month in the weeks before your period and are very intense, get it checked, because it may be premenstrual dysphoric disorder.

### Does lack of sleep affect mood?

A great deal. A meta-analysis of 64 studies found that sleep loss increases bad mood and, above all, reduces good mood, and that a night without sleep worsens bad mood more than losing a few hours.

### Is there a test for mood swings?

There is no specific one, because mood swings are a symptom with many causes. The bipolar disorder test explores them most directly, and the ADHD, depression and insomnia tests help complete the picture.