Biological explanations of OCD
What are the characteristics of someone with
Obsessive-compulsive disorder (OCD)?
OCD is an anxiety disorder. The
behaviours are ritualistic, (hand
washing, constant checking) and is
therefore is the source of great
Interestingly the disorder is equally
common in both men and women
and the onset of the behaviour is
usually in young adult life.
Again you could think of the
disorder as having two components
Obsessions – recurrent, intrusive thoughts or
The obsessions generally cause anxiety as they are
unlike the sufferers typical thoughts. These
thoughts are believed to be uncontrollable, the
sufferer feels as though they may lose control and
act upon these obsessions. The most common
obsessions take the form of
Compulsions – Repetitive acts that work to
These behaviours can be ‘hidden’ i.e. mental acts
or overt i.e. hand washing.
The vast majority of sufferers realise their
behaviour is irrational but feel compelled to
perform the given behaviour for fear of
something terrible occurring, thus the behaviour
also create anxiety.
impulses that are perceived as inappropriate,
grotesque or forbidden (DSM-IVR).
reduce anxiety of the sufferer by preventing some
dreaded event happening (DSM-IVR).
What are the characteristics of someone with
Obsessive-compulsive disorder (OCD)?
A diagnosis is given if the sufferer fits the following
Recurrent persistent thoughts, impulses or images that feel
intrusive and inappropriate, and cause excessive anxiety or
The sufferer partakes in regular repetitive behaviour
(hand washing). The behaviour must not be related in anyway to
what they are designed to prevent.
The individual recognises the behaviour is excessive and
product of their own mind.
Biological explanations of OCD.
Genetic Factors (A01)
Family/Twin Studies- Nestadt et al (2000) 80
patients with OCD & 343 of their near relatives
compared with 73 control patients without mental
illness & 300 of their relatives. Strong link with
near family (5x greater risk if had first degree
Meta-analysis of 14 twin studies found on average MZ
twins 2x more likely to develop the disorder if
their co-twin had it than DZ twins.
COMT gene COMT helps to reduce the action of
dopamine. The variation in the COMT gene
decreases the amount of COMT available and
therefore dopamine is not controlled and there is
probably too much. Researchers collected DNA
samples from 73 people with OCD and 148 who
did not have a mental disorder. The variation in
the gene occurred in nearly half of the men with
OCD but only 10% of women with OCD. It was
found in about 17% of those with good mental
Evaluation of genetic factors (AO2)
+ Concordance rates for twin studies generally high compared with other
disorders (e.g.. 87%)
+The OCD symptoms of parents and their children are often different which
suggests the disorder is not learned.
-However, concordance rates are never 100% which means that OCD is not
entirely genetic.
+ COMT gene- study by Schindler confirmed association but didn’t find gender
differences found previously.
-Research rarely replicated as this is a new area
+/-Other genes being discovered all the time – unlikely to be just one gene.
- Studies before 1990 difficult to interpret due to differences in diagnostic
-Problems with twin studies – they may not be truly identical. Problems with bias
in diagnosis.
-Difficulties in separating effects of environment and genetics.
Biochemical Factors
Serotonin – Lower levels of serotonin found in OCD
sufferers .
Dopamine levels are thought to be abnormally high
in people with OCD- thus suggesting other
neurotransmitters are involved in OCD.
Evaluation of biochemical factors
+Studies using drugs have shown a reduction in dopamine levels is positively
correlated with a reduction in OCD symptoms.
+Experiments which inject animals with drugs that increased levels of dopamine
have caused the animals to demonstrate OCD type behaviours.
+Drugs that increase serotonin (anti depressants have been shown to reduce
OCD symptoms.
- But research results relating to serotonin are varied – sometimes symptoms have
been made worse. There is a great deal of contradictory research.
- Drugs seem to show only partial alleviation of the symptoms so the process is
not fully understood. The exact function of neurotransmitters in the
development of OCD is far from understood.
-Cause or effect- it may be that neurotransmitter levels fluctuate as a result of
OCD rather than as a cause of it.
Brain Dysfunction
Basal Ganglia –abnormalities in prefrontal cortex where
thinking and judgement takes place is often present in
OCD sufferers.
OCD is often found in cases of Tourette’s and
Parkinson’s disease which are all disorders in which the
basal ganglia is implicated.
Basal ganglia damage resulting from head injuries can also
cause OCD.
Surgery which disconnects the basal ganglia from the
frontal cortex can reduce symptoms of severe OCD
Brain Dysfunction
Another area implicated is the OFC circuit. The
OFC sends ‘worry’ signals. These signals are
normally suppressed by the caudate nucleus. In
OCD the caudate nucleus is thought to be
damaged so it cannot suppress the signals which
become increasingly excited – increasing
compulsive behaviour and anxiety.
Evaluation of neuroanatomy
Basal ganglia and OFC:
+Neuro imaging studies have shown increased activity in basal
ganglia in OCD sufferers.
- However results of neuro imaging studies have been inconclusive
and basal ganglia impairment has not been found in all OCD
+ Scans show increased activity in OFC in OCD patients.
+ It has been demonstrated that OFC damage caused by head
injury, viruses and tumours can give rise to OCD.
+ Menzies (2007) supported both neuroanatomical and genetic
explanations – make notes on the study (207)
Evaluation of biological explanations
Promising research but cannot yet offer a
complete explanation.
One of most powerful challenges to this view is
that PSYCHOLOGICAL interventions show a
strong therapeutic effect and yet do not rely on
drugs or make any physical intervention.
Examination questions on biological
January 2010
 Outline one biological and one psychological explanation for obsessive compulsive
disorder (9)
 Evaluate explanations for obsessive compulsive disorder (16)
June 2010
Not examined -Psychological therapies and clinical characteristics
January 2011
Psychological explanations of OCD
Freud –OCD arises when unacceptable wishes and impulses from
the ID are only partially repressed and so provoke anxiety. The
use of ego defence mechanisms reduce the anxiety. The 3 most
common defences in terms of OCD are:
isolation ( people attempt to isolate themselves, or disown
undesirable thoughts and impulses. When the forces of the ID
dominate, the impulses intrude as obsessional thoughts.
undoing ( when isolation fails the second defence of ‘undoing’
produces compulsive acts-washing away unacceptable impulses)
reaction formation (taking on traits that are opposite to the
unacceptable impulses-such as compulsive kindness may be a
way of countering unacceptable aggressive impulses.)
Inferiority complex explanation
Some parents dominate their children and prevent them from
developing a sense of their own competence. When this happens
an inferiority complex may result so that later, as adults, these
people may adopt compulsive rituals such as tidying out drawers,
in order to carve out an area in which they exert control of
something and can feel competent.
Psychological explanations of OCD
+ Freud used the evidence of Rat Man to support his
- Some researchers have suggested that the therapy
developed by Freud (Psychoanalysis) may have a
negative effect on OCD recovery.
- -Difficult to test the idea of unconscious
motivations. No convincing evidence to support
the PD view of OCD and psychoanalysis has been
of little help in helping people to overcome OCD.
Psychological explanations of OCD.
Mowrer suggested that the learning of fears is
a two step process:
Classical conditioning A neutral stimulus becomes
associated with anxiety through Classical
Operant conditioning Any action that enables the
individual to avoid a negative event is negative
reinforcement. Avoidance of the fear leads to
positive outcomes and is therefore reinforced.
Thus the compulsive behaviour becomes a
way of establishing control and reducing
anxiety- and as a result the behaviour is
reinforced and the behaviour may become
compulsive whenever the individuals face
thoughts that provoke anxiety.
Psychological explanations of OCD.
Behavioural evaluation AO2
+ Researchers thought that if Mowrer was right, that OCD patients are
predisposed to more rapid conditioning. Research did support this finding, OCD
patients were conditioned more rapidly.
+Further research (Rachman) has shown that compulsions do relieve the anxiety of
obsessional thoughts. In a series of experiments OCD patients were asked to
carry out some ‘prohibited’ activity such as touching something dirty. Patients
were then allowed to carry out their compulsion (showed reduction in anxiety).
If however they were asked to delay carrying out their compulsive activity their
anxiety levels were found to persist for a while then gradually decline.
Compulsions therefore provide a quicker relief from anxiety.
+ This theory has led to development of a reasonably effective therapy –ERP.
- Theory does not explain the CAUSE of the obsessive thoughts, it explains how
they are maintained. (e.g. aspirins might cure headaches but headaches are not
due to lack of aspirin in the body!)
Cognitive explanations of OCD
 Everyone has unwanted or intrusive thoughts from time to time
but these thoughts can be ignored or dismissed fairly easily.
 For some people irrational thoughts cannot be ignored and feel
overwhelming leading to the expectation that terrible things will
 The thoughts continue because the person cannot ignore them.
 This is also because they often have depression.
 In order to avoid the consequences of these thoughts the
sufferer must ‘neutralise’ them. This only provides temporary
relief and then the anxiety builds up again.
 Over time people become more convinced that these thoughts
are dangerous and they become obsessions.
 The need to reduce the anxiety they cause becomes a
Evaluation of cognitive explanations
of OCD
+ Research has supported the idea that people with OCD have
different patterns of thinking, such as believing that they should
have total control over their world.
+Research has also shown that people with OCD have more
intrusive thoughts than ‘normal’ people.
+The Rachman research also supports the cognitive explanation as
well as the behavioural explanation.
+ CBT therapies have been shown to be reasonably effective in
treating OCD.
-the theory is more descriptive than explanatory – why do people
develop OCD in the first place? We all have intrusive thoughts
but don’t all get OCD.
No single explanation can account for a complex disorder like
Likely to be an interaction between biological, psychological and
social factors.
Diathesis stress model- certain individuals have an underlying
biological predisposition to OCD. This may develop fully in
response to environmental triggers.