Intrusive Thoughts and Obsessive-Compulsive Disorder (OCD): Symptoms and Treatment

Since the classic 1978 paper by Rachman and de Silva it has been known that unwanted, intrusive thoughts and images also occur in people without mental disorders, and their content can resemble the obsessions seen in OCD. The difference usually lies not in which thoughts appear but in how often they return, how much anxiety they cause, how they are interpreted and how the person reacts to them.

How should this be understood? Experiencing isolated intrusive thoughts is common — in the NCS-R study more than 25% of people had at some time had obsessions or compulsions — whereas OCD is diagnosed in a few percent. A strange, disturbing thought alone (for example ‘what if I hurt someone?’) therefore means neither illness nor a hidden wish, nor danger. In people without OCD such a thought is usually dismissed as meaningless and quickly disappears; in OCD it is perceived as threatening, which fuels anxiety and prompts rituals.

Obsessions are recurrent, intrusive thoughts, images or impulses that cause marked anxiety or discomfort and that the person tries to get rid of or neutralize. Compulsions are repetitive behaviours (washing, checking, arranging, counting) or mental acts (repeating phrases, ‘cancelling’ a bad thought with a good one, repeated analysing) performed to reduce anxiety or prevent a feared event. Compulsions bring temporary relief but in the longer run strengthen obsessions, because they teach the brain that the thought really was dangerous and the ritual protected.

Important for understanding: in OCD the person usually understands that the fears are excessive, although at that moment they feel compulsion and intense anxiety (the degree of insight varies). The content of obsessions is often contrary to the person’s own values — which is precisely why it is so distressing. The belief that a person with intrusive thoughts about aggression is dangerous is misleading. Clinical experience indicates that such a thought arouses disgust, not a wish to act, and that people with OCD usually avoid situations in which they might harm someone. Any worry on this matter is nevertheless worth discussing with a specialist.

Perfectionism, conscientiousness or liking order are not OCD until they cause distress and take up a lot of time (the diagnostic criteria usually refer to more than an hour a day) or disrupt functioning. The difference lies, among other things, in that a personality trait is often consistent with the person’s values and gives a sense of satisfaction, whereas obsessions and compulsions are experienced as unwanted and exhausting.

The diagnosis is made by a psychiatrist or clinical psychologist on the basis of a history, often with structured scales (for example the Y-BOCS). Laboratory tests do not confirm OCD, but may be ordered to rule out other causes of anxiety symptoms, such as thyroid disease or the effects of drugs.

The best-documented psychotherapy for OCD is cognitive behavioural therapy with exposure and response prevention (ERP). It involves gradual, planned confrontation with situations or thoughts that provoke obsessions while refraining from the ritual, so that anxiety can subside by itself and the brain learns that the feared consequences do not arrive.

An older meta-analysis (Olatunji et al., 2013; 16 randomized trials, 756 participants) showed that cognitive behavioural therapy outperformed control conditions after treatment (Hedges’ g = 1.39) and at follow-up (g = 0.43), with a smaller effect against placebo than against a waiting list. The conclusions of the three papers are consistent: psychotherapy with an exposure component has documented efficacy, and SSRIs and clomipramine also work, but in the trials the effect of drugs is usually smaller than that of psychotherapy (with the caveat described above).

Important caveats: results differ between studies, and comparing psychotherapy with drugs is difficult, because many therapy participants were taking drugs at the same time. The choice of method — therapy alone, a drug alone or a combination — depends on symptom severity, the availability of a therapist and the patient’s preferences and is a decision made together with a doctor. We do not encourage changing or stopping drugs on your own. We did not check the availability of ERP therapy or reimbursement in Poland, so we do not give such information.

Those close often try to help by taking part in rituals or providing reassurance. Although this stems from care, it may unknowingly maintain the disorder. In such a situation it is worth consulting a therapist on how to support a person with OCD without reinforcing the obsessions.

What we do not cover: OCD in children and adolescents, which requires a separate approach, advanced methods in treatment resistance (for example neuromodulation) or details of drug dosing. We also do not describe hypotheses linking OCD to infections, because the evidence is ambiguous.

For someone who has just noticed tormenting, recurring thoughts, the most important thing is reliable knowledge: the phenomenon is widespread, and when it becomes a disorder it is one of the better described in psychotherapy, with a specific method tested in trials. The hardest part can be overcoming shame and fear of judgement, so it is worth remembering that specialists know these symptoms and talking about them does not mean someone is dangerous.