Depression is a disorder that causes persistent feelings of low mood, low energy and reduced enjoyment of activities. It affects people of all ages and from all backgrounds.
Pathophysiology
The pathophysiology is not fully understood and involves a mix of complex mechanisms. At least in part, it involves a disturbance in neurotransmitter activity, particularly serotonin (5-hydroxytryptamine, or 5-HT).
The cause is often described as “a chemical imbalance” or “low levels of serotonin”, which may be helpful as a simple explanation but is probably overly simplistic.
Causes
Depression may be triggered by life events (e.g., the loss of a loved one). However, it can occur without any apparent triggers. It is thought to be caused by genetic, psychological, biological and environmental factors. Having an affected relative is a significant risk factor.
Physical health conditions can trigger or exacerbate depression, and it commonly occurs with conditions such as chronic pain conditions (e.g., migraines or juvenile arthritis), asthma, type 1 diabetes and epilepsy.
Presentation
Symptoms of depression should be present for at least two weeks before considering a diagnosis. The core symptoms of depression are:
- Low mood
- Anhedonia (a lack of pleasure or interest in activities)
Emotional symptoms include:
- Irritability
- Anxiety
- Low self-esteem
- Guilt
- Hopelessness about the future
Behavioural symptoms include:
- Avoiding social situations (e.g., school)
- Clinginess
- Withdrawing (e.g., alone with phone)
Cognitive symptoms include:
- Poor concentration
- Poor school performance
Physical symptoms include:
- Low energy (tired all the time)
- Abnormal sleep (particularly early morning waking)
- Poor appetite or overeating
- Unexplained symptoms (e.g., abdominal pain)
There are key points that need to be considered in assessing children and adolescents with depression. Particular attention needs to be given to the psychosocial contributors. Ask questions with the child on their own, as well as taking a history with parents or carers present.
- Potential triggers (e.g. loss of a family member)
- Home environment
- Family relationships
- Relationship with friends
- Sexual relationships
- School situations and pressures
- Bullying
- Drugs and alcohol
- History of self-harm
- Thoughts of self-harm or suicide
- Family history
- Parental depression
- Parental drug and alcohol use
- History of abuse or neglect
Management
For mild depression in children and adolescents, management involves:
- Watchful waiting
- Health promotion (e.g., healthy diet, exercise, sleep, avoiding alcohol and engaging with hobbies)
- Follow-up after 2 weeks
- Psychological interventions (e.g., CBT)
For moderate to severe depression:
- Referral to CAMHS
- Psychological interventions (e.g., CBT)
- SSRI medications (if not responding to psychological therapy)
For children and adolescents, fluoxetine is the first-line medication for depression. Sertraline and citalopram are considered second-line. Medication is continued for at least 6 months after remission.
Admission may be required where there is a high risk of self-harm, suicide or self-neglect or where there may be an immediate safeguarding issue.
Last updated February 2026
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