Key Features:
Persistent Sadness: Feeling sad, empty, or hopeless most of the day, nearly every day.
Loss of Interest or Pleasure: Anhedonia, or a loss of interest or pleasure in activities that were once enjoyable.
Changes in Appetite or Weight: Significant changes in appetite or weight, either overeating and weight gain or appetite loss and weight loss.
Sleep Disturbances: Insomnia, where individuals have difficulty falling asleep or staying asleep, or hypersomnia, where individuals sleep excessively.
Fatigue or Loss of Energy: Feeling tired, lethargic, or lacking energy, even after rest.
Feelings of Worthlessness or Guilt: Experiencing feelings of worthlessness, self-blame, or excessive guilt.
Difficulty Concentrating or Making Decisions: Problems with concentration, decision-making, or memory.
Psychomotor Agitation or Retardation: Restlessness or agitation, or slowed movements and speech.
Suicidal Thoughts or Behavior: Thoughts of death or suicide, suicide attempts, or self-harming behaviors.
Physical Symptoms: Physical symptoms such as headaches, digestive problems, or chronic pain may also be present.

Types of Depression:
Major Depressive Disorder (MDD): This is the most common form of depression and involves experiencing symptoms of depression for most of the day, nearly every day, for at least two weeks.
Persistent Depressive Disorder (Dysthymia): Persistent Depressive Disorder involves a chronic, long-term form of depression lasting for at least two years. Symptoms may be less severe than in MDD but are present most of the time.
Bipolar Disorder (Bipolar Depression): Bipolar Disorder involves periods of both depression and mania (elevated mood). During depressive episodes, symptoms are similar to those of MDD.
Seasonal Affective Disorder (SAD): SAD is a subtype of depression that occurs seasonally, typically during the fall and winter months when there is less sunlight.
Postpartum Depression (PPD): PPD occurs after childbirth and involves symptoms of depression that can range from mild to severe.
Premenstrual Dysphoric Disorder (PMDD): PMDD involves severe mood symptoms that occur in the week before menstruation and significantly interfere with daily functioning.
Psychotic Depression: Psychotic depression involves severe depressive symptoms accompanied by psychotic features such as hallucinations or delusions.
Atypical Depression: Atypical depression is characterised by mood reactivity, meaning individuals experience an improved mood in response to positive events or situations.
Treatment-Resistant Depression: Some individuals do not respond to standard treatments for depression and may have treatment-resistant depression, requiring alternative or adjunctive treatments.