Obsessive-Compulsive Disorder

Obsessive-Compulsive Disorder (OCD) is an anxiety-related condition characterised by persistent, intrusive thoughts (obsessions) and repetitive behaviours or mental acts (compulsions) performed to reduce the anxiety caused by the obsessions. OCD affects approximately 1–2% of the population and can be severely debilitating. For AQA A-Level Psychology, you need to understand the characteristics of OCD, both biological and psychological explanations, and biological and psychological treatments.

Key Definition: Obsessive-Compulsive Disorder (OCD) is a mental health condition characterised by obsessions (recurrent, unwanted, intrusive thoughts, images, or urges that cause anxiety) and compulsions (repetitive behaviours or mental acts that the person feels compelled to perform to reduce the anxiety caused by the obsessions).

---

Characteristics of OCD

OCD is characterised by three components:

Component	Description
Emotional	Persistent anxiety and distress caused by obsessive thoughts; feelings of guilt, disgust, or shame; significant psychological discomfort if compulsions cannot be performed
Behavioural	Compulsive behaviours — repetitive actions performed to reduce anxiety (e.g., hand-washing, checking, counting, ordering). These behaviours are excessive and not realistically connected to the threat they are designed to neutralise. The person may also avoid situations that trigger obsessions.
Cognitive	Obsessive thoughts — recurrent, intrusive, unwanted thoughts, images, or urges (e.g., thoughts of contamination, harm to self or others, symmetry, forbidden or taboo thoughts). The person recognises that these thoughts are irrational but cannot stop them. Catastrophic thinking about the consequences of not performing compulsions.

Common Types of Obsessions and Compulsions

Obsession Type	Example	Related Compulsion
Contamination	Fear of germs, dirt, or bodily fluids	Excessive hand-washing, cleaning, avoidance of "contaminated" objects
Harm	Fear of harming oneself or others (e.g., stabbing, poisoning)	Checking (e.g., repeatedly checking the stove is off, the door is locked)
Symmetry and order	Need for things to be perfectly aligned, balanced, or in a specific order	Arranging and ordering objects; counting
Forbidden thoughts	Intrusive sexual, religious, or aggressive thoughts that the person finds repulsive	Mental rituals (e.g., repeating prayers, counting to neutralise the thought)
Hoarding	Fear of losing important items or needing something in the future	Collecting and being unable to discard objects

Key Definition: Obsessions are recurrent, persistent, intrusive thoughts, images, or urges that the person experiences as unwanted and that cause marked anxiety or distress. Compulsions are repetitive behaviours or mental acts that the person feels driven to perform in response to an obsession, according to rigid rules, or to prevent a dreaded event.

---

Biological Explanation of OCD

Genetic Factors

There is strong evidence for a genetic component to OCD. Research suggests that OCD runs in families and that certain genes may increase vulnerability to the disorder.

Key research:

Nestadt et al. (2010) conducted a meta-analysis of genetic studies of OCD and concluded that OCD has a significant genetic component. They reported that first-degree relatives of people with OCD are five times more likely to develop the disorder than people without a family history of OCD.

Study	Findings
Nestadt et al. (2010)	First-degree relatives of OCD patients are 5x more likely to develop OCD
Pauls et al. (1995)	Concordance rate for OCD is higher in MZ twins (68%) than DZ twins (31%)
Taylor (2013)	Meta-analysis: OCD is polygenic — multiple genes each contribute a small amount to risk

Candidate genes:

• COMT gene — Codes for the enzyme catechol-O-methyltransferase, which breaks down dopamine. One variant of the COMT gene (the low-activity variant) leads to higher levels of dopamine, which has been associated with OCD.
• SERT gene (5-HTT) — Codes for the serotonin transporter, which is responsible for the reuptake of serotonin from the synapse. Mutations in the SERT gene may reduce serotonin activity, contributing to the obsessive and anxious symptoms of OCD.

Neural Explanations

The biological explanation of OCD also involves abnormalities in brain structure and neurochemistry.

Serotonin Hypothesis: Low levels of serotonin have been implicated in OCD. Serotonin is a neurotransmitter involved in mood regulation, and reduced serotonin activity in certain brain circuits is thought to contribute to the obsessive and compulsive symptoms of OCD. This hypothesis is supported by the effectiveness of SSRIs (which increase serotonin levels) in treating OCD.

Brain Structure Abnormalities:

Research using brain imaging techniques has identified abnormalities in specific brain regions in people with OCD:

Brain Region	Normal Function	Abnormality in OCD
Orbitofrontal cortex (OFC)	Decision-making, error detection, recognising when something is "wrong"	Overactivity — heightened error signals lead to the persistent feeling that something is wrong or incomplete, driving obsessive thoughts
Caudate nucleus	Part of the basal ganglia; acts as a filter, suppressing repetitive thoughts and behaviours	Dysfunction — fails to suppress the repetitive loop of obsessive thoughts, allowing them to persist
Thalamus	Relay centre for sensory information	Overactivity — may contribute to the heightened awareness and anxiety associated with OCD

Menzies et al. (2008) compared brain scans of OCD patients, their close relatives without OCD, and healthy controls. They found that both OCD patients and their relatives had reduced grey matter in key brain regions (including the orbitofrontal cortex and the right inferior frontal gyrus), compared with controls. The fact that unaffected relatives also showed these structural differences suggests a genetic vulnerability to OCD that affects brain development.

Evaluation of the Biological Explanation

Strengths:

• Twin studies and family studies provide strong evidence for a genetic component (higher concordance in MZ twins than DZ twins).
• Brain imaging studies consistently show abnormalities in the OFC-caudate-thalamus circuit.
• The effectiveness of SSRIs in treating OCD supports the role of serotonin.
• Menzies et al.'s finding that relatives of OCD patients show similar brain differences (even without OCD) supports a genetic/neural basis.

Limitations:

• OCD is polygenic — no single gene causes OCD. Multiple genes, each with a small effect, interact with environmental factors. The genetic contribution is complex and not fully understood.
• Concordance rates in identical twins are not 100%, indicating that environmental factors also play a significant role. If OCD were purely genetic, concordance in MZ twins would be 100%.
• Brain imaging studies are correlational — they show associations between brain differences and OCD, but cannot prove that brain abnormalities cause OCD. The abnormalities could be a consequence of the disorder or of medication.
• The serotonin hypothesis is an oversimplification. Other neurotransmitters (e.g., dopamine, glutamate) are also implicated in OCD, suggesting a more complex neurochemical picture.