Biological Approach to Explaining OCD

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Obsessive Compulsive Disorder

OCD is also classed as an anxiety disorder

Typically begins in young adult life and has two main components - obsessions and compulsions

Obsessions are persistent thoughts and compulsions are repetitive behaviours

Emotional Characteristics

Both obsessions and compulsions are source of considerable anxiety and distress

Sufferers are aware that behaviour is excessive and this causes feelings of embarrassment and shame

Cognitive Characteristics

Obsessions are recurrent, intrusive thoughts or impulses that are perceived as inappropriate or forbidden

May be frightening and/or embarrassing so person doesn't want to share them

Thoughts, impulses or images aren't simply excessive worries about everyday problems

Seen as uncontrollable, which creates anxiety

Person recognises that obsessional thoughts or impulses are product of their own mind

At some point during the course of disorder, person does recognise that obsessions or compulsions are excessive or unreasonable

Behavioural Characteristics

Compulsive behaviours are performed to reduce anxiety created by obsessions

Repetitive and unconcealed, such as hand washing checking

May be mental acts such as praying or counting

Patients feel they must perform these actions

i.e. compelled to perform these actions otherwise something dreadful might happen

Creates anxiety

Behaviours aren't connected in a realistic way with what they are designed to neutralise or prevent and are clearly excessive

Some patients only experience compulsive behaviours with no particular obsessions

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Genetic Explanations

The COMT gene

May contribute to OCD

Involved in production of catechol-O-methyltransferase

Regulates production of dopamine that has been implicated in OCD

All genes come in different forms (alleles) and one form of COMT gene has been found to be more common in OCD patients than people without

Variation produces lower activity of COMT gene and higher levels of dopamine (Tukel et al)

The SERT gene

SERT gene (5-HTT) which affects transport of serotonin, creating lower levels of this

Lower levels are implicated in OCD

One study found a mutation of this gene in two unrelated families where six of seven family members had OCD (Ozaki et al, 2003)

Lower levels of SERT gene means dopamine can't be inhibited

Diathesis-Stress

Each individual gene only creates a vulnerability (diathesis) for OCD as well as other conditions, such as depression

Other factors ("stressors") affect what condition develops or indeed whether any mental illness develops

Therefore some people could possess the COMT or SERT gene variations but suffer no ill effects

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Neural Explanations

Abnormal Levels of Neurotransmitters

Dopamine levels are thought to be abnormally high in people with OCD

Based on animal studies - high doses of drugs enhance levels of dopamine induce stereotyped movements resembling compulsive behaviours found in OCD patients (Szechtman et al 1998)

Lower levels of serotonin are associated with OCD

Conclusion is based on fact that antidepressant drugs that increase serotonin activity have been shown to reduce OCD symptoms (Pigott et al 1990)

Antidepressants that have less effect on serotonin don't reduce OCD symptoms (Jenicke, 1992)

High levels of dopamine, low levels of serotonin

Abnormal Brain Circuits

Several areas in frontal lobes of brain are thought to be abnormal in people with OCD

Caudate nucleus (located in basal ganglia) normally suppresses from orbitofrontal cortex (OFC)

OFC sends signals to thalamus about things that are worrying

When caudate nucleus is damaged, it fails to suppress minor "worry" signals and thalamus is alerted, which in turn sends signals back to OFC, acting as worry circuit

Supported by PET scans of patients with OCD, taken while symptoms are active --> show heightened activity in OFC

Serotonin and dopamine are linked to these regions of frontal lobes

Comer (1998) reports serotonin plays a key role in operation of OFC and caudate nuclei, and therefore it would appear abnormal levels might cause areas to malfunction

Dopamine is also linked to this, as it's main neurotransmitter of basal ganglia

High levels of dopamine lead to over-activity of this region (Sukel, 2007)

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Evaluation

Family and Twin Studies

Evidence for genetic basis comes from studies of first-degree relatives (patients or siblings) and twin studies

Nestadt et al (2000) identified 80 patients with OCD and 343 of first- degree relatives --> compared them with 73 control patients without and their relatives

Found first-degree relative with OCD had a five-times greater risk of having illness themselves at some point

Meta-analysis of 14 twin studies of OCD found that, on average, identical (MZ) twins were more than twice as likely to develop OCD if their co-twin had disorder than case for non-identical twins (DZ) (Billet et al 1998)

Concordance rates are never 100% which means that environmental factors must play a role too (diathesis-stress model)

Occurrence of OCD that seems to run in families rather than specific symptoms which shows that there's at least an environmental contribution in terms of symptoms

Tourette's Syndrome and Other Disorders

Pauls and Leckman (1986) studied patients with Tourette's and their families

Concluded that OCD is one form of expression of same gene that determines Tourette's

Obsessional behaviour of OCD and Tourette's is also found in children with autism

Obsessional behaviour is typical of anorexia nervosa, and is one of characteristics distinguishing individuals with anorexia with bulimia

Furthermore, reported that two out of every three patients with OCD also experience at least one episode of depression (Rasmussen and Eisen 1992)

Supports view that there's not one specific gene or genes unique to OCD but they merely act as a predisposing factor towards obsessive-type behaviour

Research Support for genes and OFC

Menzies et al (2007) used MRI to produce images of brain activity in OCD patients and their immediate family members without OCD

And also a group of unrelated healthy people

OCD patients and their relatives had reduced grey matter in key regions of brain --> supports view that anatomical differences are inherited and these may lead to OCD in certain individuals

Menzies et al concluded that, in future, brain scans may be used to detect OCD risk

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Further Evaluation

Real-World Application

Mapping of human genome has led to hope that specific genes could be linked to particular mental and physical disorders

Mother's eggs could be screened for specific genes, thus giving parents choice of whether to abort those eggs with the gene

Alternatively, gene therapy may produce means of turning genes "off" so that a disorder isn't expressed

This presumes that there's a relatively simple relationship between a disorder and genes

As we have suggested it's likely there isn't a straightforward link --> this is an issue for genetic explanations because they lull people into thinking that there may be simple preventative measures

Alternative Explanations

Two-process model can be applied to OCD

Initial learning occurs when neutral stimulus is associated with anxiety --> maintained through avoidance

Thus obsession is formed and then a link is learned with compulsive behaviours which reduce anxiety

Supported by success of treatment of OCD called exposure and response prevention which is fairly similar to systematic desensitisation

Patients have to experience their feared stimulus and at same time are prevented from performing their compulsive behaviours

Studies have reported high success rates, for example, Albucher et al (1998) report that 60-90% of adults with OCD have improved considerably using ERP