Depression

Depression is more than sadness. It is a group of conditions that affect mood, thinking, and the ability to function—and it is highly treatable.

What is depression?

Depressive disorders all share a common core: a persistent sad, empty, or irritable mood accompanied by changes in thinking and physical functioning that significantly affect a person's ability to go about daily life. What varies between the different types is how long they last, when they occur, and what causes them.

Types of depressive disorders

Major Depressive Disorder (MDD)

The most recognised form of depression. MDD involves discrete episodes lasting at least two weeks, though most episodes last considerably longer. During an episode, there are clear changes in mood, thinking, and bodily functions such as sleep, appetite, and energy. The disorder is recurrent in the majority of cases, meaning episodes tend to return over time, with periods of remission in between.

Persistent Depressive Disorder

A more chronic form of depression in which depressed mood persists for at least two years in adults, or at least one year in children and adolescents. It combines what were previously separate diagnoses—chronic major depression and dysthymia. The symptoms may be less intense than MDD but their prolonged nature makes them particularly disruptive to daily life.

Disruptive Mood Dysregulation Disorder (DMDD)

A diagnosis that applies to children up to 12 years of age, characterised by persistent irritability and frequent episodes of extreme behavioural dyscontrol—outbursts that are out of proportion to the situation. Children with DMDD typically go on to develop unipolar depressive disorders or anxiety disorders in adulthood, rather than bipolar disorder.

Premenstrual Dysphoric Disorder (PMDD)

A specific form of depression tied to the menstrual cycle. Symptoms begin sometime after ovulation and remit within a few days of menstruation. PMDD has a marked impact on functioning and is recognised as a treatment-responsive condition distinct from general premenstrual tension.

Substance/Medication-Induced Depressive Disorder

Depression that arises as a direct result of using substances of abuse or taking prescribed medications. A wide range of substances and medications can produce depression-like symptoms, and addressing the underlying cause is a key part of treatment.

Depressive Disorder Due to Another Medical Condition

Depression that is the direct physiological consequence of a medical condition—such as hypothyroidism, Parkinson's disease, or stroke. Identifying and treating the underlying medical condition is central to managing this form of depression.

Other Specified Depressive Disorder

Used when depressive symptoms cause real distress or impairment but do not fully meet the criteria for a more specifically defined depressive disorder. Named presentations include recurrent brief depression, short-duration depressive episodes, and episodes with insufficient symptoms.

Unspecified Depressive Disorder

Used when depressive symptoms are clearly present and causing distress or impairment, but a more specific diagnosis cannot be made at that time—for example, in emergency settings where full information is not yet available—or when the clinician has not documented why the full criteria are not met.

Unspecified Mood Disorder

The broadest provisional mood disorder category, used when significant mood symptoms are present but it is not yet possible to determine whether the presentation is depressive or bipolar in nature. Often used in acute or emergency settings where full history is unavailable.

Signs and symptoms

The specific symptoms of depression vary by type, but common signs across depressive disorders include:

Persistent sad, empty, or hopeless mood
Irritability or frustration, even over small matters
Loss of interest or pleasure in activities once enjoyed
Changes in appetite—eating significantly more or less than usual
Sleep disturbances—insomnia or sleeping too much
Fatigue and low energy
Difficulty thinking, concentrating, or making decisions
Feelings of worthlessness or excessive guilt
In severe cases, thoughts of death or suicide

Depression and grief

It is important to distinguish between normal grief—such as the sadness following bereavement—and a major depressive episode. Grief can involve intense suffering, but it does not typically develop into a depressive disorder on its own. When bereavement and depression do occur together, symptoms tend to be more severe, functional impairment is greater, and the outlook without treatment is worse. People who develop depression following a loss often have other vulnerabilities to depressive disorders.

What helps

Depressive disorders respond well to treatment. Most people see significant improvement with the right support. Common approaches include:

Cognitive Behavioural Therapy (CBT)—helps identify and change negative thought patterns and behaviours that maintain depression
Medication—antidepressants such as SSRIs and SNRIs are effective for many people, particularly in moderate to severe depression
Behavioural activation—gradually reintroducing meaningful activities to counter withdrawal and low motivation
Lifestyle factors—regular exercise, consistent sleep routines, and reducing alcohol can meaningfully improve mood
Social support—connection with trusted people and peer support groups plays an important role in recovery

The most effective approach is often a combination tailored to the individual. A mental health professional can help you find what works best.

When to seek help

Consider reaching out to a professional if low mood, lack of interest, or other symptoms have been present for more than a couple of weeks, or if they are affecting your work, relationships, or daily functioning. Depression is not a sign of weakness, and you do not need to wait until things feel unbearable. Early support leads to better outcomes.