Subthreshold depressive symptoms

Patients with subthreshold depressive symptoms (eg persistent depressive disorder) have either:

• symptoms that are insufficient to warrant a diagnosis of major depression
• residual symptoms of a partially treated major depressive episode
• persistent mild depressive symptoms associated with comorbidities such as personality disorder.

Consider differential diagnoses in patients presenting with depressive symptoms. Thoroughly assess patients with depressive symptoms, including an assessment of suicide risk.

Persistent depressive disorder (dysthymic disorder) is defined as enduring and often fluctuating, low mood of at least 2 years duration (or 1 year for children) with no more than 2 months without symptoms. Symptoms are insufficient to meet the criteria for major depression but patients may experience episodic exacerbations of symptoms.

Although patients do not meet the criteria for major depression, they still experience psychological distress. Use shared decision making with the patient to decide whether to start treatment for subthreshold depressive symptoms.

The principles of treating subthreshold depressive symptoms are the same as those for major depression (see Principles of treating major depression in adults and young people or Principles of treating major depression in children); however, psychosocial interventions are first line and the use of antidepressants is not routine.

After a benefit–harm analysis, consider using an antidepressant if the patient has:

• symptoms that are persistent, cause significant functional impairment and have not responded to psychosocial interventions
• a history of major depression, particularly if severe or recurrent.

For advice on choosing an antidepressant, see Approach to antidepressant therapy for major depression in adults and young people or Initial pharmacological treatment of major depression in children.