PHQ 9 is a self report diagnosis tool that evaluates the severity of depressive symptoms based on criteria from the DSM-IV guidelines. The patient is asked to review the past two weeks in respect to experiencing the following:

■ Losing interest in activities usually performed with pleasure.

■ Experiencing feelings of hopelessness, depression.

■ Sleep problems from falling asleep to too much sleep.

■ Lack of energy and feeling exhausted.

■ Eating disorders from lack or too much appetite.

■ Feelings of disappointment and lack of confidence.

■ Lack of concentration in simple actions.

■ Restlessness or extreme fatigue.

■ Self-harm or suicidal thoughts.

Each of the nine items are rated on the following scale:

■ Not at all (0 points);

■ Several days (1 point);

■ More than half the days (2 points);

■ Nearly every day (3 points).

The criterion and construct validity of the scale was assessed in 3,000 primary care patients. The main criticism of the tool relates to the fact that it is not very specific in regards to suicidal ideation.

Result interpretation

The overall PHQ-9 score result ranges between 0 and 27. Patients scoring closer to 0 are less likely to exhibit symptoms associated with depression, whilst patients scoring closer to 27 are experiencing severe depressive symptoms.

The table below introduces the 4 severity stages and clinical recommendations:
PHQ9 Score Severity Recommendations
0 - 4 None No specific recommendations
5 - 9 Mild Monitoring symptoms
10 - 19 Moderate Referring for treatment
20 - 27 Severe Starting treatment and monitoring

The cut off values are at 5, 10 and 20 points. Scores above 10 are considered to indicate moderate to severe depression with 88% sensitivity and 88% specificity.