Mental Health Calculators

What mental health screening covers, and the questions these tools answer

Mental health covers emotional, cognitive and behavioural wellbeing: mood disorders, anxiety disorders, trauma-related disorders, substance use, attention difficulties and general psychological distress. Because these conditions are diagnosed clinically, standardised questionnaires play a special role: they make symptoms countable, comparable over time, and communicable between patient and clinician. Every tool in this library is a validated screening instrument, widely used in both clinical practice and research.

Mood and anxiety are covered by the best-known instruments. The PHQ-9 scores the nine DSM criteria for depression over the previous two weeks, producing both a severity band and, crucially, a direct question about thoughts of self-harm. The GAD-7 does the same for generalised anxiety across seven items. The WHO-5 measures positive wellbeing rather than symptoms, and low scores flag the need for further assessment. The K10 captures non-specific psychological distress, useful as a broad first screen. The EPDS screens for postnatal depression, designed for the perinatal period when ordinary depression scales can mislead.

Specific conditions have dedicated tools. The PCL-5 maps directly onto the DSM-5 criteria for post-traumatic stress disorder across intrusion, avoidance, negative mood and arousal symptom clusters. The MDQ screens for the lifetime history of manic or hypomanic symptoms that suggests bipolar disorder. The ASRS v1.1 screener identifies adult ADHD symptoms, and the SPIN questionnaire measures social anxiety. Substance use is covered by the AUDIT for alcohol and the DAST-10 for drugs, both designed to grade the spectrum from hazardous use to possible dependence.

When clinicians, students and the public use these calculators

In primary care these questionnaires are the workhorses of mental health assessment: a PHQ-9 and GAD-7 at presentation, repeated at follow-up to measure response to treatment. Perinatal services use the EPDS at routine contacts. Addiction services use the AUDIT and DAST-10 to grade substance use and guide brief interventions or referral. Psychiatrists use the PCL-5 and MDQ as structured adjuncts to clinical interviews, and occupational health and counselling services use the K10 and WHO-5 as broad wellbeing screens.

Members of the public increasingly use these tools for self-screening, and that is a legitimate use when handled honestly: a high score is a reason to seek professional assessment, not a diagnosis to carry alone. Students and researchers use the instruments to learn psychometric assessment and to collect standardised outcome data. Across all settings, the questionnaires work best as the start of a conversation, giving patient and clinician a common set of numbers to discuss.

Interpreting results: what the scores change in practice

Each instrument has commonly used severity bands. On the PHQ-9, scores of 0 to 4 suggest minimal depression, 5 to 9 mild, 10 to 14 moderate, 15 to 19 moderately severe, and 20 to 27 severe, with 10 often used as the threshold for clinically significant depression warranting active treatment. The GAD-7 follows a similar structure for anxiety. These bands guide the intensity of response: watchful waiting and self-help resources for mild scores, structured psychological therapy for moderate scores, and combined treatment approaches for severe scores, always individualised.

Some items matter beyond their points. A positive response to PHQ-9 question 9, concerning thoughts of death or self-harm, requires prompt clinical assessment of suicide risk regardless of the total score; it should never be left for a routine follow-up. On the AUDIT, scores of 8 or above suggest hazardous or harmful drinking meriting brief intervention, while scores of 20 or above suggest possible dependence and the need for specialist referral. An EPDS score of 13 or above commonly prompts further assessment for postnatal depression, with lower thresholds sometimes used when clinical concern exists. A WHO-5 score at or below 50 suggests poor wellbeing and indicates that depression screening is warranted.

Change over time is often more informative than a single score. A PHQ-9 falling from 18 to 9 shows treatment is working even though symptoms remain; a score that does not move after an adequate trial of treatment suggests the plan needs changing. This is why clinicians repeat these measures: they turn the vague question of whether someone is getting better into something that can be tracked.

Limitations and pitfalls: what these tools cannot do

The central limitation is also the most important: these are screening instruments, not diagnostic interviews. A high PHQ-9 does not diagnose major depressive disorder, and a low score does not exclude it; diagnosis requires clinical assessment of the full picture, including history, functioning and exclusion of medical causes. The MDQ in particular is known for false positives when used as a general screen, and positive results need careful clinical follow-up rather than a bipolar label.

Scores are influenced by more than the disorder they target. Physical illness, pain, poor sleep and medication effects inflate somatic items on depression and anxiety scales; grief can mimic depression; cultural and language factors shape how questions are understood and answered. Self-report bias cuts both ways: some people minimise symptoms from stigma or fear of consequences, others amplify them in distress. A questionnaire completed in crisis may look very different two weeks later, which is why timing and context belong in the interpretation.

These tools also have safety limits. They must never be used alone to assess suicide risk: a negative question 9 does not guarantee safety, and risk assessment is a clinical skill involving direct conversation. Scores should not be used to make employment, legal or insurance decisions without proper clinical governance. And while self-screening is valuable, anyone in distress, anyone with thoughts of harming themselves, and anyone whose daily functioning is impaired should seek professional help promptly rather than relying on a questionnaire.

How to use this library

Answer each question honestly and with reference to the stated time period, usually the past two weeks; rushing or answering aspirationally produces a misleading score. Read the severity band together with the interpretation notes, and treat the result as information to bring to a clinician, not a conclusion to act on alone. If you are screening yourself, consider what the score is telling you: mild symptoms may respond to self-help and lifestyle measures, while moderate or severe scores, or any thoughts of self-harm, merit professional assessment. Like all our calculators, your answers are processed in your browser and never leave your device. If you are in crisis, contact your local emergency services or a crisis helpline immediately rather than completing questionnaires.

Related specialities

These calculators are often used alongside tools from neighbouring fields:

• Psychiatry
• Neuro-Psych
• Neurology
• Geriatrics

Frequently asked questions