OCD ( biological explanation + treatment)

(16 marker) can write either neural or genetic explanation or both

A01( serotonin+ brain structures)

The neural explanation for OCD focuses on the role of the nervous system, particularly neurotransmitters and brain structures. Abnormal levels of neurotransmitters have been found in people with OCD. For example, dopamine levels are abnormally high, and this has been specifically linked to the compulsive behaviours characteristic of OCD, as dopamine is associated with reward and repetitive actions. In contrast, serotonin levels are abnormally low in OCD sufferers, which affects mood regulation and increases anxiety and obsessive thinking. This explanation is supported by the success of antidepressant drugs, which increase serotonin activity and have been shown to reduce OCD symptoms, suggesting serotonin plays a causal role. In addition, there are abnormalities in brain circuits and structure, particularly within the orbitofrontal cortex (OFC) and basal ganglia. The OFC, located in the lateral frontal lobes, is responsible for logical thinking and decision-making, but these circuits appear to be impaired in OCD sufferers. When the OFC sends worry signals to the thalamus, the basal ganglia should filter them, but in OCD this system malfunctions, resulting in persistent and intrusive thoughts and repetitive compulsions.

A03 ( strength- supporting evidence) 

P: There is supporting evidence for the neural explanation from research highlighting the role of serotonin in OCD.

E: Studies have found that antidepressant drugs which specifically increase serotonin activity are effective in reducing OCD symptoms. For example, Pigott et al. (1990) found that SSRIs, which enhance serotonin transmission, significantly reduced symptoms in many OCD patients. In contrast, Jenicke (1992) reported that antidepressants with little effect on serotonin levels did not reduce OCD symptoms.

E: This indicates that serotonin plays a causal role in OCD, because symptoms only improve when serotonin levels are enhanced or increased.

L: Therefore, this evidence supports the neural explanation, reinforcing the view that low serotonin levels play a key role in its symptoms.  Thus  adding  scientific credibility to the biological explanation of OCD.

A03 ( supporting evidence on brain structures)

P (Point): There is supporting evidence that abnormalities in brain structures are involved in OCD.

E (Evidence): Menzies et al. (2007) used MRI scans to compare brain structure in OCD patients, their immediate family members without OCD, and unrelated healthy controls. They found that both OCD patients and their close relatives had reduced grey matter in key brain regions, including the orbitofrontal cortex (OFC).

E (Explain): This suggests that structural differences in the OFC may be an inherited risk factor and could contribute to the development of OCD, indicating that brain anatomy plays a role in the disorder.

L (Link): Therefore, these findings support the view that not only anatomical differences may lead to OCD in certain individuals but also that these are inherited.

AO1 ( Treating OCD)  SSRI

Drug therapy for OCD aims to correct neurotransmitter imbalances, particularly low serotonin. SSRIs (Selective Serotonin Reuptake Inhibitors), such as Prozac, work by preventing the re-uptake of serotonin after it is released from the presynaptic neurone and binds to receptors on the postsynaptic neurone. This enables serotonin to remain active at the synapse, continuing to stimulate the postsynaptic neurone and making neurotransmission more effective, which reduces OCD symptoms. If SSRIs are ineffective, tricyclic antidepressants or SNRIs (Serotonin-Noradrenaline Reuptake Inhibitors) may be prescribed; both block the re-uptake of serotonin and noradrenaline, but are usually second-line treatments due to more severe side effects. Drug therapy is often used alongside CBT to maximise overall effectiveness.

A03 ( strength )

P: A major strength of drug therapy is that it has been shown to be effective in reducing OCD symptoms.
E: For example, Soomro et al. (2009) reviewed 17 studies and found that SSRIs were significantly more effective than placebos in improving symptoms, especially when combined with CBT.
E: This suggests that increasing serotonin levels can effectively reduce anxiety and compulsions in most patients, supporting the biological basis of OCD and the practical usefulness of this treatment.
L: Hence, drug therapy provides a reliable and evidence-based treatment option that can improve the quality of life for many OCD sufferers.

A03 ( Side Effects and Reductionism (Limitation))

P: However, drug therapy has several limitations, including side effects and its reductionist nature.

E: SSRIs can cause side effects such as nausea, insomnia, and sexual dysfunction, which may lead some patients to stop taking the medication. Moreover, focusing solely on biological factors ignores the role of learning and cognitive processes, such as irrational beliefs that maintain OCD  or maladaptive thinking patterns.

E: This reductionist approach oversimplifies OCD, as it fails to account for the interaction between biological and psychological influences in the disorder.

L: Therefore, although drug therapy can reduce symptoms, a holistic approach combining both medication and psychological treatment, such as CBT, is likely to be the most effective long-term solution.