**L12 - Biological Explanations of Obsessive Compulsive Disorder

Question 1

what is the MAIN ASSUMPTION of the BIOLOGICAL APPROACH to EXPLAINING OCD?

Answer 1

The BIOLOGICAL APPROACH to explaining OBSESSIVE COMPULSIVE DISORDER assumes that OCD is CAUSED BY GENETIC and BIOCHEMICAL FACTORS

Question 2

what are GENETIC EXPLANATIONS OF OCD? - PT 1

Answer 2

OCD has been CLASSED AS POLYGENIC; this means that ONE SINGLE GENE is NOT RESPONSIBLE FOR THE DISORDER

Instead, as many as 230 GENES MIGHT BE RESPONSIBLE FOR CAUSING OCD, and they are KNOWN AS CANDIDATE GENES

The COMT GENE may have a ROLE IN CAUSING OCD. This gene REGULATES THE PRODUCTION OF A NEUROTRANSMITTER CALLED DOPAMINE, which in HIGH LEVELS is ASSOCIATED WITH OCD.

Question 3

what are GENETIC EXPLANATIONS OF OCD? - PT 2

Answer 3

One VARIATION of the COMT gene results in HIGHER LEVELS of DOPAMINE. This variation has been found to be MORE COMMON in OCD PATIENTS than in people who DO NOT HAVE THE DISORDER

A SECOND GENE IMPLICATED IN OCD is the SERT GENE. This gene AFFECTS THE TRANSPORTATION OF SEROTONIN, CAUSING LOWER LEVELS OF SEROTONIN. LOW LEVELS OF SEROTONIN have been LINKED TO OCD

Question 4

+ NESTADT (EVALUATION OF GENETICS EXPLANATIONS)

Answer 4

+ NESTADT SUPPORTS the GENETIC EXPLANATION FOR OCD.

He found that PEOPLE WHO HAVE A FIRST DEGREE RELATIVE who ALREADY HAD OCD, were FIVE TIMES MORE LIKELY TO ALSO GET THE DISORDER

Question 5

+ BILLETT (EVALUATION OF GENETICS EXPLANATIONS)

Answer 5

+ BILLETT SUPPORTS THE IDEA that OCD is TRANSMITTED GENETICALLY

He found from a META ANALYSIS of 14 TWIN STUDIES that OCD is TWICE AS LIKELY TO BE CONCORDANT (inheriting the same disorder) in IDENTICAL (monozygotic) twins compared with NON IDENTICAL (dizygotic) twins

Question 6

• NOT 100% (EVALUATION OF GENETICS EXPLANATIONS)

Answer 6

• a criticism of the GENETIC EXPLANATION is that the CONCORDANCE RATE for OCD in IDENTICAL TWINS is NOT 100%.

Therefore OCD CANNOT BE CAUSED ENTIRELY BY GENETIC FACTORS

Question 7

what are NEURAL EXPLANATIONS of OCD? - PT 1

Answer 7

DOPAMINE and SEROTONIN are NEUROTRANSMITTERS that AFFECT MOOD.

ABNORMAL LEVELS of these NEUROTRANSMITTERS are ASSOCIATED with ABNORMAL TRANSMISSION OF MOOD RELATED INFORMATION.

OCD sufferers gave HIGH LEVELS of DOPAMINE. HIGH DOPAMINE LEVELS have been linked to HYPERACTIVITY in the BASAL GANGLIA area in the BRAIN. This cause REPETITIVE MOTOR FUNCTIONS (e.g compulsions)

Question 8

what are NEURAL EXPLANATIONS of OCD? - PT 2

Answer 8

SEROTONIN plays a KEY ROLE in OPERATING THE CAUDATE NUCLEUS in the BASAL GANGLIA of the BRAIN, and it seems that LOW LEVELS of SEROTONIN cause the CAUDATE NUCLEUS to MALFUNCTION.

In particular LOW LEVELS OF SEROTONIN RESULT IN OBSESSIONS

Question 9

+ ANTI DEPRESSANTS (EVALUATION OF NEURAL EXPLANATIONS)

Answer 9

+ ANTI DEPRESSANT DRUGS INCREASE SEROTONIN LEVELS in OCD PATIENTS, and this has LEAD TO A REDUCTION IN OCD SYMPTOMS

Therefore there is GOOD EVIDENCE to suggest that LOW LEVELS OF SEROTONIN COULD BE A CAUSE OF OCD

Question 10

• CAUSE OR EFFECT? (EVALUATION OF NEURAL EXPLANATIONS)

Answer 10

• a disadvantage of the NEURAL EXPLANATIONS is that NEUROTRANSMITTERS such as DOPAMINE and SEROTONIN MIGHT NOT NECESSARILY CAUSE OCD.

Instead LOW LEVELS OF SEROTONIN and HIGH LEVELS OF DOPAMINE might be a SYMPTOM OF OCD

CAUSE AND EFFECT of OCD CANNOT BE CLEARLY ESTABLISHED using this EXPLANATION, the research does not comprehensively answer whether the NEUROTRANSMITTER LEVELS CAUSE OCD or THEY ARE CAUSED BY OCD