Biological approach: OCD

Introduction to OCD

• obsessions and compulsions

OCD’s an anxiety disorder characterised by obsessions and compulsions.According to DSM- 5 the diagnosis requires both:

1)Obsessions: recurrent and persistent thoughts which are intrusive and unwanted.

• lead to anxiety and distress

• these are neutralised through another thought or action called a compulsion

2)Compulsions: repetitive behaviour or mental act done in response to obsessions in order to reduce anxiety

• its often excessive and can be unrealistic

OCD: behavioural characteristics

1) Compulsion’s are repetitive: People feel compelled to repeat behaviour as a response to their obsessive thoughts, ideas and images

2) Compulsions reduce anxiety: Vast majority of compulsive behaviours are performed in an attempt to manage anxiety produced by obsessions, and performing these helps

OCD: emotional characteristics

1) Anxiety and distress: obsessive thoughts are unpleasant and frightening and the anxiety that goes with it can be overwhelming. The urge to repeat a behaviour is what causes anxiety

2)Guilt and disgust: OCD often involves irrational guilt. E.g. over minor moral issues. Or it may cause disgust towards external objects like dirt

OCD: cognitive characteristics

1) Recurrent and persistent thoughts: Constantly experience repeated obsessive thoughts, images and ideas of an intrusive nature. They are uncontrollable and cause distress

2)Insight into excessive anxiety: Those with OCD are aware that their obsessions and compulsions aren’t rational. In fact, this awareness is necessary for the diagnosis (if someone believed that their obsessive thoughts were based on reality that would be a different mental disorder). However, in spite of this, they still feel catastrophic thinking about worst case scenarios should their anxieties be justified

3)Selective attention: Increased awareness of the source of their obsessions in new situations. Also, have increased awareness of certain stimuli (causing obsessions) while ignoring equally relevant stimuli)

4)Hyper vigilance: May be constantly on the lookout for threats (both real and imagined). May be hyper-aware of their surroundings, scanning for potential dangers at all times

5) Catastrophic thinking: May assume the worst will happen if they don’t perform their compulsions

Explaining OCD

• what are the 2 explanations

• genetic explanation

• neural explanation (neurotransmitters and brain circuits)

Explaining OCD

• Genetic explanation

This explanation centres around the fact that OCD is inherited through genetic transmission. We get it from our parents and it is acquired from specific genes being passed on. These genes increase the likelihood of having OCD and are known as ‘candidate genes’(causing vulnerability)

1)Candidate genes: specific genes leading to vulnerability for OCD (OCD candidate genes)

• 5-HTT gene is a faulty SERT gene and is responsible for the transportation of serotonin (inhibitory neurotransmitter)

• inheriting a defective version of the 5-HTT gene means transportation of serotonin is disrupted, leading to low levels in the synapse

Ozaki et al: found mutation of the 5-HTT gene in a family where 6/7 member’s had OCD. Shows that it’s linked to a mutated/defective gene

2)Polygenic: Other researchers argue that OCD is a polygenic disorder, meaning several genes contribute to it’s acquisition

Taylor: Did a meta-analysis and found evidence of up to 230 different genes involved in OCD (this show’s it’s polygenic)

Explaining OCD

• Genetic explanation

  • Evaluation

Strengths:

Supporting evidence from twin studies: Nestadt et al

• reviewed previous twin studies into OCD and found 68% CR MZ twins and 31% CR for DZ twins. This show’s that as the proportion of shared genes increase, so does the likelihood of both twins developing OCD. Therefore, OCD is due to genetic factors and is inherited

Weakness:

Simplistic & diathesis stress model might offer a better explanation

• According to this model, certain genes leave the individual more vulnerable to OCD, but whether an individual develops it is influenced by environmental triggers

• Cromer et al: found over ½ OCD patients in their sample had a traumatic experience in their past, and OCD was more severe for those with more than 1 trauma

• Shows it cannot be entirely genetic and traumatic events may act as a contributory trigger to start OCD tendencies. We need to consider both environmental and genetic factors to be more holistic in our understanding

Explaining OCD

• Neural explanation

  • Evaluation (AO3)

Strengths:

Practical application in development of SSRI’s

Weakness:

Supporting evidence is correlational

Explaining OCD

• Abnormal levels of NT

Low level’s of serotonin cause OCD. Serotonin is involved in regulating mood by facilitating synaptic transmission between neurons

• Those with OCD, the serotonin is removed too quickly from the synapse, so there’s no chance to pass on a signal. Therefore it can’t regulate mood

• These low levels are what lead to mood issues associated with OCD

Also, dopamine levels are abnormally high in OCD patients and this is linked to their anxiety and the inability to stop focusing on their obsessive thoughts

Explaining OCD

• Abnormal brain circuits

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

1)Orbitofrontal cortex: sends worry signals to the thalamus(both major and minor). These worry signals are then mediated by the caudate nucleus within the basal ganglia

• This caudate nucleus then acts as a filter as suppresses the minor signals from the OFC and let’s through the major signals to the thalamus

• Once the thalamus has altered to the worry signals, it initiates a response/reaction.

2)In someone with OCD, the problem lies with their caudate nucleus because its hypersensitive and instead of suppressing minor worry signals, both major and minor pass through to the thalamus

3)Thus, the thalamus confirms and receives these minor signals too, creating a worry circuit, leading to them acting on their worries in the form of compulsions

Treating OCD

• Drug therapy

Drug therapy target’s abnormal neurotransmitter levels

SSRI’s: E.g. Prozac

Since OCD is due to low levels of serotonin, SSRI’s seek to increase level’s of serotonin in the synapse. This regulates mood and decreases anxiety caused by OCD

This works by:

• they block the reuptake of serotonin into the pre-synaptic neuron, thus leaving more serotonin in the synapse.

• More serotonin influences the activity of the post-synaptic neuron by prolonging the activation of serotonin and makes transmission of inhibition signals to the next neuron easier

• This addresses deficiency of serotonin in the synapse for those with OCD

• ¾ months of daily use

SRI’s: Tricyclics

• works the same as SSRI’s but is less selective in their action

• Do this by blocking the mechanism for reuptake of serotonin and into the pre-synaptic neuron

• used when SSRI’s aren’t effective

Treating OCD

• strengths

Treating OCD

• weaknesses