The biological model of psychological disorders

The biological model views psychological disorders, such as obsessive-compulsive disorder (OCD), as physical illnesses with underlying physical causes.

This approach suggests that these conditions are fundamentally similar to physical ailments like a common cold, differing mainly in their prominent psychological symptoms.

Genetic factors in obsessive-compulsive disorder (OCD)

The biological approach proposes that genetics may contribute to the development of OCD. Research has explored whether having a close family member with OCD increases an individual's likelihood of developing the condition.

Evidence supporting genetic factors

• Twin studies - A meta-analysis by Billet et al. (1998) revealed that identical twins showed a 68% concordance rate for OCD, meaning if one twin had OCD, the other was likely to have it in 68% of cases. This rate dropped to 31% for non-identical twins.
• Family studies - Pauls et al. (2005) discovered that around 10% of individuals with an immediate family member (parent, sibling, or child) with OCD also had the disorder, compared to just 2% in the general population.

Evidence challenging genetic factors

• Incomplete concordance - No research has shown a 100% concordance rate, even among identical twins, suggesting that genetics alone cannot fully explain OCD. Other influences, such as observing and copying behaviours from relatives, might play a role.
• Broader anxiety link - High concordance rates may reflect a genetic predisposition to general anxiety rather than OCD specifically. Additional factors, like biochemical or psychological triggers, could determine whether OCD develops.

Biochemical factors linked to OCD

Another biological explanation for OCD focuses on imbalances in brain chemistry, particularly involving the neurotransmitter serotonin. Studies using brain imaging have identified lower serotonin levels in individuals with OCD.

Evidence supporting biochemical factors

• Effectiveness of SSRIs - Insel (1991) found that selective serotonin reuptake inhibitors (SSRIs), drugs that boost serotonin levels, reduced OCD symptoms in approximately 50-60% of patients.
• Consistent findings - Zohar et al. (1996) reported similar results, with SSRIs alleviating symptoms in about 60% of OCD sufferers.

Evidence challenging biochemical factors

• Partial effectiveness - SSRIs do not work for all patients, with a significant number showing no improvement, indicating that serotonin imbalance is not the sole factor in OCD.
• Correlation vs. causation - The relationship between low serotonin levels and OCD is correlational, meaning it is unclear whether reduced serotonin causes OCD or is a result of the condition.

Neurological factors associated with OCD

Neurological research suggests that abnormalities in specific brain regions, particularly the basal ganglia, may be linked to OCD. The basal ganglia are located deep within the brain.

Evidence supporting neurological factors

• Brain injury studies - Max et al. (1994) observed higher rates of OCD in individuals who had suffered head injuries leading to damage in the basal ganglia.
• Activity patterns - Research has shown increased activity in the basal ganglia during thoughts or behaviours associated with OCD.
• Related conditions - OCD often appears alongside other disorders affecting the basal ganglia, such as Parkinson's and Huntington's disease.

Evidence challenging neurological factors

• Inconsistent findings - Aylward et al. (1996) found no notable difference in basal ganglia impairment between OCD patients and those without the condition.
• Partial association - Not all individuals with OCD exhibit basal ganglia damage, indicating that this factor cannot account for every case of the disorder.

Strengths and weaknesses of the biological explanation for OCD

Strengths of the biological explanation

• Scientific grounding - The approach is rooted in observable biological evidence, such as correlations between low serotonin levels or basal ganglia abnormalities and OCD symptoms.
• Genetic research support - Twin and family studies demonstrate that genetics play a partial role in the likelihood of developing OCD.
• Ethical perspective - By treating OCD as a physical illness, this approach avoids blaming individuals for their condition, framing it as a medical issue rather than a personal failing.

Weaknesses of the biological explanation

• Neglect of environmental factors - This model overlooks the potential impact of upbringing, social surroundings, and personal experiences, which other psychological approaches consider crucial.
• Ethical concerns with treatment - Biological treatments, such as drug therapy, can raise issues like dependency and may focus on managing symptoms rather than addressing underlying causes.

Biological treatments for OCD using drug therapy

The biological approach to treating OCD primarily relies on drug therapy, focusing on correcting chemical imbalances in the brain. The most common treatment involves selective serotonin reuptake inhibitors (SSRIs), a type of antidepressant that increases serotonin availability.

SSRIs work by preventing the reabsorption of serotonin in the synaptic cleft, the gap between neurons, ensuring more serotonin is available to transmit signals to the next neuron.

Advantages of drug therapy

• Proven effectiveness - Thoren et al. (1980) found that SSRIs significantly outperformed placebos in reducing obsessive thoughts among OCD patients.
• Specificity to serotonin - Research indicates that other antidepressants, which do not target serotonin, are generally ineffective for OCD.

Disadvantages of drug therapy

• Limited success rate - Up to 50% of OCD patients do not experience symptom improvement with SSRIs. Even among those who do, as many as 90% relapse when they discontinue the medication.
• Delayed results - Patients often need to take SSRIs for several weeks before noticing any reduction in symptoms.
• Side effects - Common side effects include nausea, headaches, and occasionally heightened anxiety, which may lead some individuals to stop taking the medication prematurely.