What causes depression?

Depression is a complex condition that rarely has a single cause. It usually develops through a combination of biological, psychological and social factors, each influencing the other.

Understanding what might be contributing to how you feel can be an important step towards getting better. It’s not your fault, and with the right support, recovery is possible.

Depression is multifactorial: the biopsychosocial model

Depression often arises when biological, psychological and social factors interact. For example, someone with a genetic vulnerability might experience depression after a major life stressor, while another person might develop it following a physical illness or prolonged stress.

These factors don’t determine your future, they simply highlight areas where support and treatment can make a difference.

Biological factors

Genetics and family history

Depression can run in families, but it isn’t purely genetic. Having a parent or sibling with depression may increase your vulnerability, but it doesn’t mean you’ll develop it too. Environment, lifestyle and coping strategies also play important roles.

Brain chemistry and hormones

Depression is linked to changes in the brain’s communication systems. Neurotransmitters such as serotonin, dopamine and noradrenaline help regulate mood, sleep and motivation. When these are disrupted, it can affect how you feel and think.

Hormonal shifts, for example, during menstruation, pregnancy, menopause or as a result of thyroid disorders, can also influence mood and energy levels.

Physical health conditions

Long-term or serious illnesses can affect both body and mind. Conditions like chronic pain, diabetes, heart disease and neurological disorders are known to increase the risk of depression. Some medications can also contribute to low mood.

Tip: If you’re worried that depression medication might be affecting your mood, speak to your GP or pharmacist before making any changes.

Psychological factors

Thinking styles and personality

Certain thought patterns or personality traits can make some people more prone to depression. These may include perfectionism, self-criticism or a tendency to dwell on negative thoughts. Low self-esteem or feeling unable to manage stress can also contribute.

Trauma and adverse experiences

Difficult or traumatic experiences, particularly in childhood, can increase vulnerability to depression later in life. This can include abuse, neglect, bullying or significant loss. Conditions such as post-traumatic stress disorder (PTSD) and complex PTSD (CPTSD) often involve depressive symptoms.

Coping behaviours

People sometimes cope with distress through avoidance, overworking, or using substances like alcohol or drugs. While these might offer temporary relief, they often worsen low mood over time.

Therapies such as cognitive behavioural therapy (CBT), dialectical behaviour therapy (DBT) and trauma-focused therapy can help identify and rework these patterns.

Social and environmental factors

Life events and chronic stressors

Major life changes or ongoing pressures can have a significant emotional impact. Common examples include:

• Bereavement or relationship breakdown
• Job loss or financial insecurity
• Discrimination or social isolation
• Caring responsibilities or burnout

Lifestyle contributors

Lack of sleep, low physical activity and poor nutrition can all influence brain chemistry and mood. Alcohol or recreational drug use can also disrupt emotional balance and increase depressive symptoms.
Seasonal changes

For some people, depression appears during the darker months when daylight hours are shorter, known as seasonal affective disorder (SAD). Light exposure, maintaining a routine and professional support can all help manage these effects.

Common triggers vs underlying vulnerabilities

Depression often develops when a trigger interacts with an existing vulnerability, for example, stress at work in someone who already has low self-esteem, or illness in someone with a family history of depression.

While you can’t always control vulnerabilities, you can learn to manage triggers and build resilience through therapy, lifestyle changes and professional support.

Myths and misunderstandings

• There isn’t one single cause of depression, everyone’s experience is different.
• It’s not just a “chemical imbalance.” Brain chemistry plays a role, but so do psychological and social factors.
• You can recover even if the causes aren’t “fixed.” Treatment helps you build coping skills, resilience and a stronger sense of wellbeing.

Life stages and groups at higher risk

Children and teenagers

Bullying, academic pressure and family conflict can contribute to depression in young people. Symptoms may appear as irritability, withdrawal or physical complaints rather than sadness.

Perinatal (antenatal and postnatal) depression

Hormonal changes, sleep deprivation and major life adjustments after childbirth can lead to perinatal depression. Both parents can be affected, not just mothers.

Menopause and hormonal transitions

During menopause, fluctuating hormone levels can affect mood and energy. The right support and treatment can make these changes easier to manage.

Older adults

Loneliness, bereavement and chronic health problems can make older adults more vulnerable to depression. Depression in later life is often overlooked, but it is highly treatable.

Men and women

Men may show irritability, anger or increased risk-taking rather than sadness, while women may experience more guilt or rumination linked to hormonal influences.

What you can do next

If you recognise some of these risk factors or triggers in your life, remember that depression is treatable and help is available.

You should seek support if:

• Your symptoms last more than two weeks
• Low mood is affecting your work, relationships or motivation
• You experience thoughts of self-harm or suicide

In an emergency:

Call 999, go to your nearest A&E, or contact Samaritans on 116 123 (free, 24/7).

Next steps:

• Speak to your GP for advice, screening or NHS self-referral
• Book a confidential Priory mental healh assessment for fast access to specialist support
• Explore therapy and lifestyle changes to build long-term wellbeing

How Priory can help

At Priory, we offer evidence-based treatment for all forms of depression. Our services include:

• Confidential mental health assessments
• Therapy (CBT, DBT, mindfulness and trauma-focused approaches)
• Medication management, where appropriate
• Inpatient, outpatient and online treatment options across the UK

Take the first step towards feeling better, book a confidential assessment today.