14th February 2025

Presentation and diagnosis of depressive disorders

Core and additional symptoms

The triad of core depressive symptoms is low mood, anergia and anhedonia (lack of enjoyment).

Additional symptoms include poor concentration, feelings of worthlessness or hopelessness, suicidal ideation, increased or decreased sleep, and decreased appetite. Depression can present with cognitive impairment (pseudodementia), which can cause diagnostic uncertainty in the older population.

Core and additional symptoms of depression can be quantified with the Hospital Anxiety and Depression Score (HADS).

Symptoms must be present for most of the day, on most days, for a period of at least 2 weeks to diagnose a depressive episode. If this occurs more than once, with resolution in between, it is a recurrent depressive disorder.

Psychotic symptoms

Depressive disorders can present with psychotic symptoms, usually only when severe. These tend to be congruent with mood. Delusions may be nihilistic, such as Cotard’s, where the individual believes that they are dead, non-existent, lacking in organs or blood, or rotting. There may be hallucinations, such as auditory hallucinations of criticising voices, olfactory hallucinations of unpleasant smells, or visual hallucinations of the devil.

Subtypes of depressive disorders

Depressive episodes are categorised according to severity (as determined by the number of core and additional symptoms), presence of somatic symptoms, and presence of psychotic symptoms. There may be accompanying symptoms of anxiety, leading to a diagnosis of depression with anxiety.

Depressive disorders also include the milder, subclinical syndromes of cyclothymia and dysthymia. Cyclothymia is a milder version of bipolar affective disorder in which high and low episodes occur but do not meet diagnostic criteria for mania or bipolar depression. Dysthymia is a milder version of recurrent depressive disorder in which low episodes occur without meeting diagnostic criteria for a depressive episode.

Differential diagnoses

Other psychiatric disorders can present similarly to depression such as adjustment disorder, post-traumatic stress disorder, anxiety disorders, eating disorders and personality disorders. The key in differentiating between them is the time course and predominance of certain features.

Organic illnesses are also important differential diagnoses. Common mimics include anaemia, dementia, Parkinson’s, stroke, Addison’s disease, hypothyroidism, menopause, hypercalcaemia, and sleep apnoea. As such, a thorough history and examination are essential, with consideration of investigations including FBC, U&Es, LFTs, TFTs, B12, folate, glucose, bone profile and morning cortisol.

Medications can also cause depressive symptoms, such as beta blockers, steroids, sedatives, interferon, oestrogen and antipsychotics. Recreational drugs such as alcohol, cannabis, cocaine and amphetamines can also be responsible.