Depression: Symptoms, Causes & Treatment

Depression, clinically known as depressive disorder, is a common and serious mental health condition. It involves persistent low mood, loss of interest in things you used to enjoy, and a range of other emotional, physical, and cognitive changes that interfere with your ability to function day to day.

Depression is not something you can simply push through. It is a medical condition with recognised causes and effective treatments.

Globally, approximately 332 million people live with depression, around 5.7% of the world's adults. It is roughly 1.5 times more common in women than in men, and it is one of the leading causes of disability worldwide. Despite how common it is, in high-income countries only about one third of people with depression receive treatment.

Depression involves changes in how your brain regulates mood, motivation, sleep, and energy. Several neurotransmitters, chemical messengers in the brain including serotonin, dopamine, and norepinephrine, play a role in depression. When these systems are disrupted, your ability to feel pleasure, stay motivated, concentrate, and sleep all become affected.

Depression is not simply a chemical imbalance in the way that phrase is sometimes used, the picture is more complex than that. It involves interactions between brain chemistry, stress hormones, sleep, inflammation, and life experience. Research has found that chronic stress can contribute to changes in brain structure and function over time, particularly in areas involved in mood regulation and memory.

These aren't changes you can simply decide your way out of. That's what makes depression different from ordinary sadness, and it often doesn't lift on its own without support.

To receive a diagnosis of depression, you typically need to have experienced five or more of the following symptoms nearly every day, for at least two weeks, and at least one of them must be depressed mood or loss of interest.

Emotional and cognitive symptoms:

• Persistent sad, empty, or hopeless mood
• Loss of interest or pleasure in activities you used to enjoy
• Feelings of worthlessness or excessive guilt
• Difficulty thinking, concentrating, or making decisions
• Thoughts of death or suicide

Physical symptoms:

• Significant changes in appetite or weight, loss or gain
• Sleeping too much, or not being able to sleep
• Fatigue and low energy, even without physical exertion
• Slowed movement or speech that is noticeable to others
• Unexplained physical symptoms such as headaches, digestive issues, or body aches

Behavioural symptoms:

• Withdrawing from social activities and relationships
• Neglecting responsibilities at work, home, or school
• Loss of motivation to do everyday tasks
• Increased use of alcohol or substances

Depression doesn't always look like sadness. Some people describe it as feeling numb, empty, or disconnected rather than visibly distressed. Others experience primarily physical symptoms, or show it as irritability rather than low mood, particularly common in men and adolescents.

If you're unsure whether what you're experiencing is depression, a validated screening tool like the PHQ-9 (Patient Health Questionnaire) is widely used by clinicians and can help you track and describe your symptoms before speaking with a healthcare provider.

Depression develops from a combination of factors, rarely from a single cause.

Genetics. Depression runs in families. If you have a first-degree relative with depression, your risk is higher. Research estimates the heritability of depressive disorders at around 30-50%.

Life experiences. Difficult or traumatic experiences, childhood abuse or neglect, loss of a loved one, relationship breakdown, financial hardship, or long-term stress, are among the most significant contributors to depression. People who have experienced major losses or trauma are at higher risk.

Medical conditions. A number of physical health conditions are associated with depression, including thyroid disorders, Parkinson's disease, heart disease, multiple sclerosis, and chronic pain. Some medications can also cause depressive symptoms as a side effect.

Hormonal changes. Changes in reproductive hormones can trigger depression in some people, including during pregnancy, after childbirth (postpartum depression), before periods (PMDD), and during perimenopause.

Personality and thinking patterns. Tendencies toward negative self-evaluation, perfectionism, or difficulty handling uncertainty can make someone more vulnerable to depression, these patterns affect how the brain processes stress.

Social isolation. Lack of meaningful connection, loneliness, and limited social support are consistently linked to higher rates of depression across age groups.

Substance use. Alcohol and certain drugs can both trigger and worsen depression. They are also commonly used as a way of coping with depressive symptoms, which often makes things worse over time.

Depression is not one condition, it encompasses several distinct disorders, each with its own profile and treatment approach. The DSM-5 recognises the following:

• Major Depressive Disorder (MDD). This is what most people mean when they say "depression." Major depressive disorder involves at least one depressive episode lasting two weeks or more, with significant impact on daily functioning. Severity can range from mild to severe. About 80-90% of people with MDD who seek treatment respond well to it.
• Persistent Depressive Disorder (PDD). Previously called dysthymia, PDD involves a chronically low mood that has lasted for at least two years. The symptoms are less intense than major depression, but the long duration can make it just as impairing. Many people with PDD have lived with it so long they believe it's simply their personality, rather than a treatable condition.
• Seasonal Affective Disorder (SAD). SAD is a form of major depressive disorder that follows a seasonal pattern, most commonly beginning in autumn or winter and lifting in spring. It is thought to be related to reduced daylight hours affecting the body's internal rhythms and serotonin levels. About 5% of US adults experience SAD. Light therapy is a first-line treatment alongside psychotherapy and, in some cases, medication.
• Postpartum Depression. More than just the "baby blues," postpartum depression is a major depressive episode that develops during pregnancy or within the first year after giving birth. It affects more than 10% of women globally in the perinatal period. It is distinct from the short-lived emotional adjustment that is common after childbirth, and it requires treatment.
• Premenstrual Dysphoric Disorder (PMDD). PMDD involves significant mood symptoms, depression, irritability, anxiety, in the days before a period, which resolve after menstruation begins. The symptoms are severe enough to interfere with daily functioning, distinguishing it from typical premenstrual syndrome (PMS).
• Bipolar Depression. People with bipolar disorder experience depressive episodes alongside periods of elevated mood (mania or hypomania). Depression in the context of bipolar disorder requires different treatment than unipolar depression, which is why an accurate diagnosis is important.
• Atypical Depression. A subtype of major depression characterised by mood that temporarily improves in response to positive events, along with increased appetite, sleeping too much, and a heavy, leaden feeling in the limbs.

Depression and anxiety are distinct conditions, but they frequently occur together, research shows that nearly half of people diagnosed with depression also have an anxiety disorder. Understanding the difference can help you describe your experience more accurately and get the right support.

• Depression is primarily present- and past-focused. If you have depression, you may feel a persistent sense of hopelessness, emptiness, or worthlessness. Rather than fearing the future, you may feel indifferent to it. Energy and motivation drop significantly, and things that used to bring pleasure no longer do.
• Anxiety is primarily future-focused. If you have anxiety, your mind tends to be preoccupied with what might go wrong, anticipating threats, worst-case outcomes, or situations you won't be able to handle. The emotional experience is dominated by fear, worry, and tension. Your body stays in a state of alertness.

Depression is often maintained by specific thought and behaviour patterns that keep it going. Recognising which patterns are active in your experience is an important part of addressing depression, not just managing symptoms, but understanding what sustains them.

Common patterns linked to depression on Renée include:

• Rumination - replaying negative events or self-critical thoughts in a loop without resolution
• Negative Self-Talk - an inner voice that is persistently critical, dismissive, or hopeless about yourself
• Withdrawal - pulling away from people and activities, which deepens isolation and low mood
• Perfectionism - standards so high that any shortcoming feels like total failure
• Emotional Suppression - pushing feelings down rather than processing them
• Helplessness - the belief that nothing you do will make a difference
• People-Pleasing - suppressing your own needs to manage others' feelings, at significant cost to yourself

Depression makes action feel harder than it is. Small, consistent steps matter even when they don't feel meaningful.

• Move your body, even briefly. Exercise is one of the most well-supported self-care strategies for depression. Even a 20-30 minute walk has been shown to have measurable effects on mood, and those effects can build over time. You don't need to feel motivated before you start, motivation often follows action.
• Keep a basic routine. Depression disrupts structure, and the absence of structure deepens depression. Keeping consistent wake and sleep times, regular meals, and at least one fixed daily activity gives your nervous system something stable to organise around.
• Stay in contact with one person. Withdrawal is a core symptom of depression, and it makes recovery harder. You don't need to explain how you're feeling, simply maintaining some contact with another person provides protective benefit.
• Limit alcohol. Alcohol is a depressant. If you're already depressed, drinking tends to worsen mood, disrupt sleep, and reduce the effectiveness of any other support you're seeking.
• Notice and name what you're feeling. Depression often creates a foggy, undifferentiated sense of "badness" that's hard to work with. Putting a more specific label on your experience, loneliness, grief, exhaustion, shame, can make it feel more manageable and give you a starting point.
• Do one small thing you used to enjoy. Even if it doesn't bring pleasure at first, behavioural activation, gradually re-engaging with valued activities, is a core component of evidence-based depression treatment. The goal is to act before you feel ready, not to wait until the motivation returns on its own.
• Get outside and into daylight. Natural light has a documented effect on mood and sleep-wake regulation. Even 15-20 minutes of outdoor light exposure during the day can make a difference, particularly if you experience seasonal dips in mood.
• Take a depression screening. If you haven't spoken to a healthcare provider yet, completing a validated tool like the PHQ-9 and bringing it to your GP or a mental health professional is a useful first step. It gives you and your provider a shared language for what you're experiencing.

Depression is one of the most treatable mental health conditions. Research shows that approximately 80-90% of people with depression who seek treatment respond well.

• Psychotherapy for depression is highly effective and is considered a first-line treatment, either alone or alongside medication.
• Cognitive Behavioural Therapy (CBT) is the most extensively researched psychotherapy for depression. A 2023 meta-analysis of 409 randomised trials, the largest ever conducted on a single psychotherapy for any mental disorder, found that CBT is significantly more effective than control conditions, with remission rates of 36% in CBT versus 15% in control groups. CBT helps you identify and change the negative thought patterns and behaviours that maintain depression.
• Behavioural Activation (BA) focuses specifically on re-engaging with valued activities to counteract withdrawal and low mood. It is particularly effective for mild to moderate depression.
• Interpersonal Therapy (IPT) addresses depression through the lens of relationships be it grief, life transitions, conflict, or social isolation.
• Mindfulness-Based Cognitive Therapy (MBCT) is well-supported for preventing depressive relapse in people who have experienced multiple episodes.
• Medication, SSRIs and SNRIs is commonly prescribed for depression, often in combination with therapy. For moderate to severe depression, the combination of medication and psychotherapy tends to be more effective than either alone. Talk to your GP or psychiatrist about whether medication may be appropriate for you.
• Specialist treatments such as transcranial magnetic stimulation (rTMS) or electroconvulsive therapy (ECT) may be considered for severe or treatment-resistant depression.

One of the most important things I tell people with depression is that waiting to feel better before taking action is part of the trap. Depression tells you that nothing will help, that you don't have the energy, that it's not worth trying. That voice is a symptom. In treatment, we work on acting alongside the depression rather than waiting for it to lift first. That's often when things start to shift.

— Rita George, Clinical Phycologist