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Mood disorders explained

Everyone has ups and downs. Here’s a gentle map of what happens when moods get stuck, swing too far or come back again and again, and what helps.

⏱ 6 min read📑 11 sections📚 16 sources✅ Reviewed October 2026

By the numbers

Mood disorders are very common. You are far from alone.

United States

21.4%of U.S. adults experience a mood disorder at some point in their lives (survey data from 2001–2003).
9.7%of U.S. adults had a mood disorder in the past year; higher for women (11.6%) than men (7.7%).
8.3%of U.S. adults, about 21 million people, had at least one major depressive episode in 2021.
4.4%of U.S. adults experience bipolar disorder at some point in their lives.

Teens

14.3%of U.S. teens aged 13 to 18 have had a mood disorder (survey data from 2001–2004).
20.1%of U.S. teens aged 12 to 17 had a major depressive episode in 2021.

World

322 millionpeople around the world have depression (WHO, 2023 estimate).
1.5×Women are about one and a half times as likely as men to have depression.
1 in 3people with depression in high-income countries get mental health treatment; many more go without.
Numbers describe groups, not you. Every person’s story is different.

What are mood disorders?

Health conditions that mainly affect your emotional state, for weeks or longer.

A mood disorder is a mental health condition that mainly affects your emotional state. It can mean long stretches of deep sadness, unusually high or irritable moods, or both. Sometimes it shows up mostly as constant anger or irritability.

Mood disorders are common, real and treatable. They are not a weakness or a character flaw, and nobody chooses to have one. With the right support, most people feel much better and live full lives.

The main members of the family

  • Bipolar conditions: bipolar I, bipolar II and cyclothymia, with highs as well as lows
  • Depressive conditions: major depression and persistent depressive disorder (long-lasting low mood)
  • Disruptive mood dysregulation disorder (DMDD): severe, ongoing irritability in children and teens
  • Hormone-linked mood changes: before periods (PMDD), around pregnancy and birth, and around menopause
  • A seasonal pattern: low (or sometimes high) moods that return at the same time each year
🔍 Myth: “You’d always know if you had a mood disorder.”Fact: some patterns are quiet and easy to miss.
Read more

Long-lasting low mood can feel like personality, and mild highs can feel like simply having a great week. Cyclothymia, for example, often goes undiagnosed.

🧪 Myth: “It’s all in your head, so a check-up is pointless.”Fact: thyroid problems and other conditions can cause mood symptoms.
Read more

Medical conditions such as thyroid problems can cause symptoms like depression or bipolar. A physical exam and tests help rule these out.

🌙 Myth: “Hormonal mood changes aren’t real.”Fact: PMDD and perinatal depression are real, treatable conditions.
Read more

PMDD can cause severe depression, irritability and tension, and perinatal depression usually doesn’t get better without treatment. Both deserve care.

🧒 Myth: “Children are just being difficult.”Fact: children and teens can have mood disorders too.
Read more

About 1 in 7 U.S. teens has had a mood disorder, and children with DMDD have severe, ongoing irritability that affects their lives.

❄️ Myth: “Winter blues are just grumpiness.”Fact: seasonal affective disorder is a type of depression.
Read more

SAD is a type of depression with a repeating seasonal pattern, lasting about four to five months a year. It can be treated.

See the Seasonal depression (SAD) guide for much more.
This guide is for learning, not diagnosing. Recognising yourself in a description doesn’t mean you have a mood disorder. People are complex, and only a qualified professional can assess what’s going on for you. Please talk to your clinical provider or therapist.
If you are having thoughts of ending your life, please reach out now: call or text 988 (U.S.), or text HOME to 741741. If a life is in danger, call 911.

Everyday moods vs a mood disorder

Ups and downs are human. A mood disorder is stronger, longer and harder to live with.

It’s normal for mood to change with what’s happening in your life. You might feel flat after bad news or buzzing after a great day. What makes a mood disorder different is how strong the mood is, how long it lasts, and how much it gets in the way of daily life.

🌤️ Everyday ups and downsUsually make sense for the situation, and pass.
Read more

Often

  • Don’t stop you managing school, work or home
  • Last hours or a few days
  • Linked to something that happened
  • Mixed with good moments
Everyday low moods still deserve kindness: rest, a walk, a chat with someone you trust.
⛈️ A mood disorderStronger, longer-lasting and disruptive.
Read more

Often

  • Changes sleep, energy, appetite or thinking, not just feelings
  • Feels out of proportion, or comes with no clear reason
  • Gets in the way of work, school, relationships or money
  • Lasts for weeks or longer, most of the day, nearly every day
  • Other people notice you seem “not yourself”
These are general differences, not a test. If you’re unsure, that’s a good reason to talk to someone, not a reason to wait.

Two quieter patterns are easy to miss. A low mood that has lasted for years can start to feel like “just my personality”. And mild highs can feel so good that people don’t see them as part of a pattern. Both are worth mentioning to a professional.

The depression family

Major depression, long-lasting low mood, and depression with psychosis.

These conditions are mostly about lows: sadness, emptiness, numbness or irritability, with changes to sleep, energy and thinking. The Depression: understanding it guide explains them in depth, with lots of practical help. Here is a quick overview.

🌀 Depression with psychosisA severe form where depression comes with hallucinations or false beliefs.
Read more

In this severe form, depression comes with delusions (strong false beliefs) or hallucinations (hearing or seeing things others don’t).

This needs prompt professional care. Contact your clinical provider today, or call or text 988. If anyone is in danger, call 911.
🌫️ Major depressionA low mood or loss of interest lasting at least two weeks and disrupting daily life.
Read more

Major depression (also called clinical depression) causes symptoms most of the day, nearly every day, for at least two weeks. It affects how you feel, think and handle daily activities. Some people have one episode; for others it returns.

See the Depression: understanding it guide for how it feels, and Living with depression day to day for what helps.
🌥️ Persistent depressive disorder (dysthymia)Milder low mood that lasts much longer, usually two years or more.
Read more

Persistent depressive disorder, once called dysthymia, means symptoms that are less severe than major depression but last much longer, usually at least two years. Because it goes on so long, people often think it’s just who they are.

The Depression: understanding it guide has a full card on long-lasting low mood, with small steps that help.
❄️ Depression with a seasonal patternLow moods that come back at the same time each year.
Read more

Seasonal affective disorder (SAD) is a type of depression that follows a repeating seasonal pattern, most often starting in late fall or early winter and easing in spring and summer.

See the Seasonal depression (SAD) guide for light, winter and what helps.

The bipolar family

Bipolar I, bipolar II and cyclothymia: highs as well as lows.

In bipolar conditions, mood moves between lows and highs. Highs can mean unusual energy, less need for sleep, racing thoughts or irritability. Everyone has ups and downs, but with bipolar the range of change can be extreme. The “Bipolar: understanding it” guide covers this in depth.

🔺 Bipolar IIncludes at least one full high (mania) lasting a week or more.
Read more

Bipolar I involves manic episodes that last at least seven days. Low (depressive) periods usually happen too.

See “Different patterns” in the “Bipolar: understanding it” guide.
🔻 Bipolar IILows plus milder highs (hypomania), without full mania.
Read more

Bipolar II involves a pattern of depressive episodes and hypomanic episodes. Hypomania is milder than mania, so it can be easy to miss.

If you’re getting help for low moods, mention any times you felt unusually energetic or needed much less sleep.
〰️ CyclothymiaFrequent milder ups and downs over a long time.
Read more

Cyclothymia is a mild form of bipolar. Mood shifts between low periods and hypomanic highs that aren’t intense enough to count as full episodes. It’s often diagnosed after symptoms have lasted at least two years (one year in children and teens).

Because it’s mild, it often goes undiagnosed. People with cyclothymia are at risk of developing bipolar disorder, so it’s worth getting support early.

Hormone-linked moods and DMDD

Before periods, around pregnancy and menopause, and severe irritability in children.

Some depression is linked to the body’s hormone changes. NIMH groups these as reproductive-related depression: premenstrual dysphoric disorder, perinatal depression and perimenopausal depression. Each has its own guide in the app, so here is just a short introduction.

🔥 Around menopauseMood changes in the years around the last period.
Read more

Perimenopausal depression is one of the hormone-linked kinds of depression NIMH describes.

See the “Perimenopause & menopause: understanding it” guide for much more on mood, sleep and brain fog in midlife.
🍼 Perinatal depressionDepression during pregnancy or after birth. More than the “baby blues”.
Read more

Perinatal depression is a mood disorder that happens during pregnancy or after childbirth. The baby blues are mild, short-lived mood changes in the first two weeks after birth. Postpartum depression is stronger or lasts longer, and usually doesn’t get better without treatment. It can be treated.

The Pregnancy & after birth guide covers pregnancy and the first year after birth in depth, including where to get help.
🗓️ PMDD (before periods)Severe mood changes in the week or two before a period.
Read more

Premenstrual dysphoric disorder (PMDD) is a more serious form of PMS. It can bring severe depression, irritability and tension in the one to two weeks before a period, easing within a few days after bleeding starts. It affects up to 5% of women of childbearing age.

The Periods, PMDD & hormones guide covers PMS and PMDD in depth. Keeping a symptom diary helps your provider understand the pattern.
🧒 Severe irritability in children (DMDD)When a child’s anger and outbursts go far beyond ordinary moodiness.
Read more

All children have grumpy days and tantrums. Disruptive mood dysregulation disorder (DMDD) is a mood disorder in which children and teens have ongoing irritability and anger, with frequent, intense temper outbursts. The symptoms are severe, show up in more than one place (like home and school), and affect daily life.

DMDD was only recognised in 2013, so there is still limited research on it. Children with DMDD are more likely to have anxiety or depression later, which is one more reason early support matters. Help often includes therapy adapted for children and teaching parents ways to manage behaviour.

See the “Kids’ mental health (ages 0–12)” guide for more on childhood struggles. A child who is always angry is often a child who is struggling, not a “bad kid”.
Hormone-linked mood changes are real health conditions, not “just hormones” and not something to push through alone. For treatment options, consult with your clinical provider.

Why do mood disorders happen?

Usually a mix of genes, brain, body and life experiences. No one is to blame.

There is rarely one single cause. Researchers think mood disorders come from several things working together. That’s why two people can go through the same hard time and react very differently.

🧠 Brain and bodyDifferences in the brain areas that handle emotion.
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Brain imaging studies have found differences in emotion-related areas, such as the amygdala, in some people with mood disorders. Hormone changes and health conditions can also play a role.

🧬 Family and genesMood disorders can run in families.
Read more

A strong family history raises the risk, which suggests that genes play a part. But having a relative with a mood disorder does not mean you will have one.

⛈️ Life and stressTrauma, ongoing stress and big life events.
Read more

Major life stress, long-term stress, trauma and childhood abuse are all linked to mood disorders. In some people, stress acts like the spark that sets off an episode.

Not every mood change starts in the mind. NIMH notes that some medical conditions, such as viruses or thyroid problems, can cause the same symptoms as depression, and thyroid disease can cause symptoms like those of bipolar disorder. Some drugs can copy or worsen mood symptoms too.

🍷 Alcohol and drugsThey can trigger, copy or worsen mood symptoms.
Read more

Alcohol and drugs can trigger or worsen mood episodes, and health services advise avoiding them when living with a mood disorder.

See the Substance use guide if cutting down feels hard.
🫀 Long-term illnessMood and physical health affect each other.
Read more

Depression often occurs alongside long-term illnesses such as diabetes, cancer, heart disease and chronic pain, and each can make the other harder. Parkinson’s disease is also linked with depression.

Tell every member of your care team about both your body and your mood.
🦋 ThyroidAn underactive thyroid can cause tiredness and depression.
Read more

The thyroid is a small gland in your neck. When it’s underactive (hypothyroidism), common symptoms include tiredness and depression. It can’t be diagnosed from symptoms alone; a blood test can help confirm it.

It’s reasonable to ask: “Could we check my thyroid?” See the Checkups, hormones & mood guide.
Nothing you did caused your mood disorder, and it isn’t a parenting failure. It’s a health condition, and help works. A check-up can rule out body causes; please consult with your clinical provider about anything medical.

Kinds of help

Talking therapies, light therapy for seasonal lows, peer support, and medical options with your provider.

Mood disorders are treatable. Help is usually tailored to the kind of mood disorder, how strong it is and what matters to you. Many people use a mix of approaches.

💡 Light therapyFor winter-pattern seasonal lows.
Read more

Light therapy means sitting in front of a very bright light box for about 30 to 45 minutes a day, usually in the morning, from fall to spring. People with certain eye conditions should check with a provider first.

The Seasonal depression (SAD) guide explains light therapy and CBT for SAD in more detail.
🩺 Medical treatment optionsTalk with your clinical provider.
Read more

There are also medical treatment options for mood disorders. These are personal decisions to make with your clinical provider, who knows your health history.

Whatever kind of care you and your clinical provider choose is valid.
🫂 Peer supportPeople with lived experience who understand.
Read more

Peer support is linked with better quality of life, more engagement with services and fewer hospital stays.

The Living well with bipolar guide lists support groups for depression and bipolar.
💬 Talking therapiesCBT, behavioural activation, IPT, problem-solving therapy and more.
Read more

The World Health Organization lists behavioural activation, cognitive behavioural therapy, interpersonal therapy and problem-solving therapy as effective psychological treatments for depression. Cleveland Clinic also lists DBT and psychodynamic therapy for mood disorders.

See the “Therapy: the basics” guide for what each one is like. The “Bipolar: understanding it” guide covers therapies made for bipolar, like social rhythm therapy.

Living well day to day

Steady rhythms, movement, connection and noticing your patterns.

Alongside professional help, daily habits can make moods steadier. None of these is a cure, and on hard days doing even one is enough.

🚫 Go easy on alcohol and drugsThey can make moods less steady.
Read more

Avoiding alcohol, nicotine and drugs is part of NIMH’s self-care advice for depression and bipolar.

⏰ Keep a steady rhythmRegular sleep, meals and activity.
Read more

Try to keep a regular bedtime and wake-up time, eat regular meals, and structure your day with a steady routine for eating, sleeping and exercise.

See the Sleep & mental health guide for help with sleep.
🚶 Move your bodyEven a short walk helps.
Read more

Physical activity reduces symptoms of depression and anxiety. NIMH notes that just 30 minutes of walking a day can boost mood.

📓 Notice your patternsA mood journal helps you and your care team see what’s happening.
Read more

Keeping a mood journal or “life chart” can help you recognise mood swings and what sets them off. Over months, you may spot links with sleep, stress, seasons or your cycle.

Try the “My month of moods” worksheet.
🤝 Stay connectedTalk to people you trust.
Read more

Connect with people and tell someone you trust how you are feeling. Do what you can, as you can, and try to put off big life decisions until you feel steadier.

Supporting someone with a mood disorder

Patience, practical help, and looking after yourself too.

When someone you love has a mood disorder, it can be confusing and worrying. You don’t need to be an expert. Steady, patient support makes a real difference.

🌿 Look after yourselfSupporters need support too.
Read more

NIMH reminds supporters to take care of their own wellbeing too. Keep your own routines and connections, and consider a family support group or counselling for yourself.

See the Supporting someone you love guide, When someone you love is depressed, and the supporter sections of the Living well with bipolar guide.
🤲 Ways to helpUnderstanding, patience and encouragement.
Read more

NIMH suggests

  • Help with practical needs, like rides to appointments
  • Invite them for walks, outings and other activities
  • Learn their triggers and watch for big mood changes
  • Offer support, understanding, patience and encouragement
  • Remind them that with time and treatment, things can get better
💬 What to saySimple words go a long way.
Read more

Try

  • “I’ve noticed you seem different lately. How are you really doing?”
  • “I’m here on the good days and the hard ones.”
  • “Would it help if I came with you to an appointment?”
  • “You’re not a burden. I want to help.”
Avoid “just snap out of it” or “everyone gets moody”. Mood disorders are health conditions, not choices.
If someone talks about suicide or you’re worried they’re not safe, take it seriously. Call or text 988 (U.S.), or text HOME to 741741. If a life is in danger, call 911.

When and where to get help

Signs it’s time to reach out, what an assessment involves, and help right now.

It may be time to reach out if…

  • A low, high or irritable mood has lasted more than a couple of weeks
  • People close to you are worried about you
  • You’re having thoughts of death or suicide
  • You’re sleeping much more or much less, or need little sleep but don’t feel tired
  • Your mood is getting in the way of work, school, relationships or money
  • Your mood seems to follow the seasons or your cycle, and it’s hard to cope

A good first step is your primary care provider, who can check for physical causes and refer you on. You can also contact a therapist, your school counsellor or an employee assistance program. Only a qualified professional can tell whether someone has a mood disorder, and which kind, because different mood disorders can look alike, especially in a low patch.

What an assessment may include

  1. A physical exam and sometimes lab tests, to rule out other causes like thyroid problems.
  2. Questions about your health history and anything you currently take.
  3. Questions about your family’s mental health history.
  4. A conversation about your moods, sleep, eating, energy and behaviour: when changes started, how long they last and how often they come.
  5. Sometimes a referral to a mental health specialist for a fuller evaluation.

Things worth bringing up

  • How long you’ve felt this way, even if it’s years
  • Times you felt unusually energetic, needed much less sleep or felt “wired”, not just the lows
  • What other people have noticed
  • Whether your mood follows the seasons or your menstrual cycle
It may help to take notes about your symptoms before the visit. The “My mood story for an assessment” and “Could my body be part of this?” worksheets are made for this. To find treatment in the U.S., you can also search FindTreatment.gov.
If you’re in crisis, call or text 988 (U.S.), or text HOME to 741741. If a life is in danger, call 911. Outside the U.S., findahelpline.com lists free crisis lines in many countries.

📝 Worksheets for this guide

Fill these in privately in the app. Your answers stay on your phone.

My month of moodsA once-a-week look back over a month. It helps you and your care team see patterns that day-to-day logs can miss, like links with seasons, your cycle or busy weeks. This is not a diagnosis.
What helps on low days and high-energy daysMake two short menus now, while you feel steady, so you don’t have to think hard when your mood shifts.
My mood story for an assessmentTaking notes before a visit helps your provider see the whole picture, including highs, patterns and family history. Share as much or as little as you like.
Could my body be part of this?Mood can be affected by physical health. Jot down what’s going on in your body to discuss at a check-up. Only your provider can check for medical causes.
My mood-steadying habits checkA weekly check on the everyday habits that help moods stay steadier. Pick just one to work on.
Learning to support someone with mood changesFor family and friends. Get clear on what you know, what you’d like to learn, and how you’ll look after yourself while you help.
🔒 Fill in privately in the Mentally United Wellness App. Free, no ads, no accounts.

Sources

  1. Cleveland Clinic. Mood Disorders
  2. National Institute of Mental Health (NIMH). Depression (publication)
  3. National Institute of Mental Health (NIMH). Depression
  4. National Institute of Mental Health (NIMH). Bipolar Disorder (publication)
  5. NHS (UK National Health Service). Cyclothymia
  6. National Institute of Mental Health (NIMH). Seasonal Affective Disorder
  7. Office on Women’s Health (womenshealth.gov). Premenstrual dysphoric disorder (PMDD)
  8. National Institute of Mental Health (NIMH). Perinatal Depression
  9. National Institute of Mental Health (NIMH). Disruptive Mood Dysregulation Disorder
  10. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH. Hypothyroidism (Underactive Thyroid)
  11. National Institute of Mental Health (NIMH). Any Mood Disorder (statistics)
  12. National Institute of Mental Health (NIMH). Major Depression (statistics)
  13. National Institute of Mental Health (NIMH). Bipolar Disorder (statistics)
  14. World Health Organization (WHO) (2026). Depressive disorder (depression) fact sheet
  15. World Health Organization (WHO). Physical activity fact sheet
  16. Mental Health America (MHA). Peer Support Research and Reports

This guide is for education and self-care. It is not a diagnosis or a substitute for professional care. Please talk to a counselor or clinical provider about your health. Reviewed October 2026.

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