Depression

Definition/diagnostic criteria Depression is characterised by persistent feelings of sadness, worthlessness, loss of interest or pleasure in activities, and changes in sleep, appetite, or energy levels.

In the WHO’s International Classification of Diseases 11th Revision (ICD-11), depression is defined as:

The presence of depressed mood or diminished interest in activities occurring most of the day, nearly every day, for at least two weeks, accompanied by other symptoms such as reduced ability to concentrate, low self-worth or inappropriate guilt, hopelessness about the future, recurrent thoughts of death or suicidal ideation, significantly disrupted or excessive sleep, significant changes in appetite, psychomotor agitation or retardation, and reduced energy or fatigue.

Traditionally, depression is divided into four sub-groups: subthreshold, mild, moderate and severe. However NICE describes less severe depression, defined as depression scoring less than 16 on the Patient Health Questionnaire (PHQ-9) scale, more severe depression scoring 16 or above, chronic depressive symptoms and psychotic depression. Bipolar disorder is dealt with separately, here and in NICE’s Depression in adults guideline (NG222).

Epidemiology Depression affects around 1 in 10 people in the UK, and around 1 in 4 over the age of 65 (of whom 85% are estimated to receive no treatment). It can manifest at any age and is more common in women. Risk factors include personality, genetic predisposition, pregnancy and childbirth, menopause, loneliness, coexisting illness, alcohol and drug dependency.

Diagnosis Patients generally present with symptoms described above, although in older people they will often present with physical symptoms or delusions rather than describing low mood. PHQ-9 is the standard scale for grading severity, and patients should always be asked about suicidal ideation.

Differential diagnosis is wide, and can include:

• Central nervous system diseases, e.g. Parkinson’s disease, dementia, multiple sclerosis.
• Endocrine disorders, e.g. hyperthyroidism, hypothyroidism.
• Drug-related conditions, e.g. cocaine abuse, side-effects of some CNS depressants.
• Infectious disease, e.g. infectious mononucleosis.
• Sleep-related disorders.
• Other psychiatric disorders, e.g. personality disorder, dysthymia, bipolar disorder.

Investigations can be useful to exclude other conditions such as thyroid disease. Focal neurological symptoms or signs are not features of depression and should prompt urgent neurological referral if found.

Treatment The management of depression involves a combination of approaches tailored to the individual patient’s needs. Exercise, meditation, mindfulness and guided self-help all give benefit, and may be all that is required in mild depression. Talking therapies such as cognitive behavioural therapy, interpersonal psychotherapy or short-term psychodynamic psychotherapy are recommended in less severe depression. NICE states:

‘Do not routinely offer antidepressants as a first-line treatment, unless that is the person’s preference. If the person has a clear preference, or experience from previous treatment to use as a guide: support the person’s choice, unless there are concerns about suitability for this episode of depression.’

In more severe depression the advice is for a similar suite of therapies, with the most suitable options arrived at after discussion with the patient. Individual cognitive behavioural therapy plus an antidepressant is recommended as the most clinical and cost-effective option. If there is no response within 4-6 weeks, shared decision-making should be used to consider switching to an alternative talking or pharmacological therapy.

If medication is felt to be appropriate, it is advised to review how well the treatment is working with the person between 2 and 4 weeks after starting, or after 1 week if it is a new prescription for a person under 25, or if there is a particular concern for risk of suicide. We should monitor concordance, side-effects and harms of treatment and suicidal ideation, particularly in the early weeks of treatment.

Patients starting on medication should be given suitable written advice including knowing who to contact if their symptoms worsen, and should always be warned of the risk of side-effects from withdrawal, which should generally be done by tapering medication gradually rather than stopping abruptly.

NICE does not make specific recommendations on which antidepressants to use, although it notes that a longer half-life reduces the risk of withdrawal effects. For most, the first choice would be an SSRI, with an SNRI the next option. Tricyclic antidepressants and monoamine oxidase inhibitors are rarely used because of side-effects or safety profile in overdosage.

In older people, the only antidepressants recommended are sertraline or, if sedation would be useful, mirtazapine (a noradrenaline and specific serotonergic antidepressant). Tricyclics should never be used in this group (including low-dose amitriptyline) because of sedation, cardiac risks and the anticholinergic burden.

Crisis team referral is recommended for people with more severe depression who are at significant risk of suicide, self-harm or harm to others, self-neglect, or complications in response to their treatment, for example older people with medical comorbidities.

Treatment-resistant depression is a rapidly evolving area, with early stage research ongoing with psilocybin, LSD, ketamine and other controversial agents. NICE gives support for electro-convulsive therapy, transcranial magnetic stimulation and vagus nerve stimulation in selected cases, and specifically advises against the use of St John’s Wort.

Prognosis In younger people, untreated depression will remit spontaneously in more than half of cases within 12 months. Overall remission with treatment is around 70%-90%, with early recognition and intervention associated with better outcomes. However, there is a 60% lifetime risk of recurrence after the first major depressive episode, 70% with two episodes, and 90% of those with three or more episodes.

In addition, people who suffer from a depressive disorder have a suicide risk of 30 times more than the general population, and approximately 15% of patients that suffer from a depressive disorder make at least one suicide attempt.

Written by Dr Peter Bagshaw, a GP and NHS Somerset CCG mental health and dementia clinical lead