Breatheasy
Major depressive disorder (MDD): symptoms, causes and treatment
Major depressive disorder, often called MDD or clinical depression, is more than feeling sad. The symptoms doctors look for, how common it is, what causes it, how it links with anxiety, and the treatments that help most people.
Breatheasy team27 October 2026 · 5 min read
Everyone feels sad or low sometimes. But depression is different. It can make getting out of bed feel impossible, drain the joy from things you love, and convince you that nothing will ever get better.
Major depressive disorder, often shortened to MDD and also called clinical depression, is one of the most common mental health conditions. It’s also very treatable. Here’s what it is and what helps.
If you’re having thoughts of ending your life, please call or text 988 (US) now, or call 911 in an emergency. You don’t have to go through this alone.
What is major depressive disorder?
MDD is a mood disorder in which low mood or loss of interest lasts most of the day, nearly every day, for at least two weeks, along with other symptoms that affect how you think, feel and function.
Symptoms of MDD
Doctors look for five or more of these, including at least one of the first two:
- Low mood most of the day, nearly every day, such as feeling sad, empty or hopeless
- Loss of interest or pleasure in most activities (anhedonia)
- Changes in appetite or weight
- Sleeping much more or much less than usual
- Feeling restless, or slowed down
- Tiredness or loss of energy
- Feeling worthless or excessively guilty
- Trouble concentrating or making decisions
- Thoughts of death or suicide
Our post on anhedonia explains loss of interest and pleasure in more detail.
How common is it?
According to the National Institute of Mental Health, an estimated 21 million US adults, about 8.3%, had at least one major depressive episode in a recent year. It was more common in women (10.3%) than men, and most common in young adults aged 18 to 25 (18.6%).
What causes depression?
There’s rarely a single cause. Depression usually comes from a mix of:
- genes and family history
- life events, like loss, relationship breakdown, money problems or trauma
- long-term stress or loneliness
- health conditions, like chronic pain, thyroid problems or other long-term illnesses
- alcohol and drug use
- some medicines
- hormonal changes, like after giving birth
Depression and anxiety
Depression and anxiety often go together. Many people have both, and one can lead to the other: long-term anxiety can wear you down into depression, and depression can make everything feel more frightening. The good news is that many treatments help both.
Treatment that works
- Talking therapy. Cognitive behavioural therapy (CBT), behavioural activation and interpersonal therapy are well-studied. Behavioural activation, which focuses on doing small, meaningful activities to lift mood, worked better than control conditions in a review of 26 trials.
- Antidepressant medicine, often an SSRI. It usually takes a few weeks to work, and a doctor can help find the right one.
- Both together, which helps many people most, especially with moderate or severe depression.
- Other options for depression that hasn’t responded to treatment, which a specialist can discuss.
Self-help that supports treatment
- Do one small thing each day that you used to enjoy, or that gives a sense of achievement, even if you don’t feel like it.
- Move a little, like a short walk. Physical activity has good evidence for improving depression.
- Keep regular sleep and wake times.
- Stay connected, even with one person.
- Go easy on alcohol, which deepens low mood.
- Be patient with yourself. Recovery usually comes in small steps.
When to get help
See a doctor if you’ve felt low or lost interest in things for more than two weeks, or if it’s affecting your daily life. You don’t need to be sure it’s depression. If you’re worried about someone else, our post on what to say to someone who is suicidal can help.
Get help right away if you’re having thoughts of ending your life. Call or text 988 (US), or call 911 if you’re in immediate danger.
Frequently asked questions
What does MDD stand for?
MDD stands for major depressive disorder, the medical name for clinical depression.
How do you get rid of depression?
For most people, a combination of treatment (talking therapy, medicine or both) and small daily steps, like activity, sleep and connection, helps depression lift. It rarely goes away by willpower alone, so getting support is important.
Is major depressive disorder permanent?
No. Many people recover fully, and most improve a lot with treatment. Some people have more than one episode in their life, and treatment and skills learned in therapy can help prevent or shorten future episodes.
What’s the difference between depression and sadness?
Sadness is a normal emotion that passes. Depression lasts at least two weeks, affects most of the day, and comes with other symptoms like loss of interest, changes in sleep and appetite, and trouble functioning.
How Breatheasy can help
Breatheasy is built for anxiety, which often comes alongside depression, but some of its tools can support you too. Ten-second check-ins and a journal help you track mood and notice small improvements, and gentle daily steps and a kind streak, with a free rest day each week, help you keep doing small things that matter. Crisis help and an emergency contact are always one tap away. Breatheasy isn’t a treatment for depression, so please talk to a doctor too. Breatheasy is coming soon to iPhone and Android.
Sources
- Depression, National Institute of Mental Health
- Major depression statistics, National Institute of Mental Health
- Depression in adults, NHS
- Behavioural activation for depression: an update of meta-analysis, Ekers and others, PLoS One, 2014
- Effectiveness of physical activity interventions for improving depression, anxiety and distress, Singh and others, British Journal of Sports Medicine, 2023
- 988 Suicide and Crisis Lifeline
