Depression Screening (PHQ-9)

What the PHQ-9 is

The Patient Health Questionnaire-9 is a nine-question self-report screening tool, published by Kroenke, Spitzer and Williams in 2001 and used in primary care worldwide. Its nine questions map onto the criteria clinicians use to recognise depression, which is why it asks about the last two weeks specifically.

It is a screening tool, not a diagnostic one. It can tell you whether it is worth speaking to someone. It cannot tell you whether you have depression — that takes a clinician, a conversation, and usually ruling out physical causes such as thyroid problems or anaemia.

Signs and symptoms

NIMH lists these as common signs. For a diagnosis of depression, symptoms need to be present most of the day, nearly every day, for at least two weeks — and at least one of them must be low mood or loss of interest.

• Persistent sad, anxious or "empty" mood
• Feelings of hopelessness or pessimism
• Irritability, frustration or restlessness
• Feelings of guilt, worthlessness or helplessness
• Loss of interest or pleasure in things you used to enjoy
• Fatigue, or feeling slowed down
• Difficulty concentrating, remembering or making decisions
• Sleeping too much, or trouble getting to sleep and staying asleep
• Appetite or weight changes
• Aches, pains, headaches or digestive problems without a clear physical cause
• Thoughts of death or suicide, or suicide attempts

Depression is not one thing

Major depression

Depressed mood or loss of interest lasting at least two weeks and interfering with daily life.

Persistent depressive disorder

Milder symptoms that continue for two years or more.

Seasonal affective disorder

Depression that follows a seasonal pattern, typically returning each winter.

Depression with psychosis

A severe form that also involves delusions or hallucinations.

Bipolar disorder

Depressive episodes alongside manic or hypomanic episodes. Not the same as depression, and treated differently.

Perinatal and perimenopausal depression

Depression during pregnancy or after birth, and around the menopause transition.

This matters because the treatment differs. A questionnaire cannot tell these apart, and bipolar disorder in particular can be made worse by treating it as ordinary depression.

What happens next

Depression is treatable. NIMH describes three main approaches: talk therapy such as cognitive behavioural therapy or interpersonal therapy; medication, which typically takes four to eight weeks to show its full effect; and brain stimulation therapies such as ECT or rTMS for depression that has not responded to the others.

A good first step is your regular doctor. They can rule out physical causes, talk through the options, and refer you on. Taking a completed questionnaire with you gives the conversation somewhere concrete to start.