Phobias and obsessive-compulsive disorder

Phobias: the two-process model

A phobia is acquired by classical conditioning — a neutral object is paired with a frightening experience — and maintained by operant conditioning, because avoidance reduces anxiety and is therefore negatively reinforced. The second half is the important half: avoidance is what stops the fear from extinguishing naturally.

Not all phobias fit

Many people with a phobia cannot recall any traumatic pairing, and phobias cluster around snakes, heights and spiders rather than around cars and electrical sockets. Biological preparedness explains this: evolution left us ready to learn fears that once mattered for survival.

Behavioural treatments

Systematic desensitisation teaches relaxation, builds a hierarchy of feared situations, and works up it in small steps — relaxation and fear cannot coexist, so a new association is learned. Flooding exposes the person to the worst situation at once until the fear response exhausts itself: faster and cheaper, but distressing and with higher dropout, so informed consent matters more.

OCD

Obsessions are intrusive, unwanted thoughts causing anxiety; compulsions are repetitive behaviours performed to reduce that anxiety. The relief is temporary, which reinforces the compulsion and produces a self-sustaining cycle.

Explaining and treating OCD

The biological account points to genetic vulnerability, low serotonin and abnormal activity in the basal ganglia and orbitofrontal cortex. Treatment is SSRIs, which are effective for many and easy to comply with, but have side effects and relapse is common on stopping. The cognitive-behavioural account targets the belief that the thought is dangerous and one is responsible for it; exposure and response prevention asks the person to face the trigger without performing the compulsion, so they learn the feared consequence does not follow.