Different explinations

• Nerve cell- biochemical explanations

  Messages are transmitted along the cell as electrical impulses
• Transmission of nerve impulses- biochemical explanations

  1. Impulse reaches the end of the cell

  2. Crosses synapse to reach next cell

  3. Chemicals called neurotransmitters are released into the synapse in response to electrical impulse

  4. Neurotransmitters diffuse across the synapse

  5. Neurotransmitters either bind with receptors on the post-synaptic cell, are broken down into enzymes or reabsorbed into the pre-synaptic cell

  6. If enough neurotransmitters bind with the post-synaptic cell, it causes new electrical impulse to be stimulated and passed along this new cell
• Biochemical explanation - depression

  • Serotonin is a neurotransmitter. When a sense is stimulated, a message will be sent along the nervous system. The message will go from one nerve cell to another until it reaches the appropriate area in the central nervous system
  • Synaptic clefts between nerve cells and these gaps need to be bridged for a passage to pass from pre-synaptic nerve cell to another post-synaptic nerve cell
  • If serotonin levels are low then serotonin molecules may be reabsorbed back into the pre-synaptic nerve cell too soon, meaning message is not passed across the gap
• Biochemical explanation - schizophrenia

  • Another neurotransmitter dopamine is believed to play a role in schizophrenia. One explanation is that there is too much dopamine being produced, another is that there are too many dopamine receptors in some specific regions of the brain
  • Supported by the fact that some drugs e.g. LSD the increase levels of dopamine lead to similar symptoms to those experiences in schizophrenia
  • Anti-psychotic drugs work by binding to the dopamine receptors preventing an overload of dopamine reaching the post-synaptic cell
• Treating depression and schizophrenia - biochemical

  Focus of restoring normal levels of neurotransmitter action for example:

  • Treating depression by blocking the reuptake of serotonin (into pre-synaptic cells) to ensure there is enough serotonin available for messages get carried along the nervous system
  • Treating schizophrenia by blocking receptors in post-synaptic nerve ells to prevent an overload of dopamine reaching the post-synaptic nerve cell
• Genetic explanation of mental illness

  • There is some evidence that mental illness can be passed from parent to child via their genes
  • Suggests that certain disorders could be passed from parents to children through genetic transmission.
  • This might be a predisposition to the disorder and would need an environmental trigger for the disorder to be displayed
  • Because half of our genes come from each parent it is possible for 1 sibling to display a disorder but not another sibling
• Gottesman and Shields - genetic explanation

  • Found that if one twin had schizophrenia then there was a 58% chance of an identical (monozygotic) twin of having it; however if the twins were not identical (i.e. they were dizygotic) then there was only a 12% chance of a twin having it
  • This study suggests that there is a strong genetic component to schizophrenia, but it also suggests that occurrences of schizophrenia cannot be explained by genetics alone
• Evolutionary explanation

  • We have inherited traits that have a positive effect on our chances of survival
  • Offered as a possible explanation for phobias, as people with a fear of spiders, snakes, heights, deep water etc might have an evolutionary advantage that enabled them to survive and reproduce as opposed to people who didn't have those traits and died before reproducing
  • It is suggested that phobias have a genetic basis to them, being passed on in the same way as other traits that give people evolutionary advantage (e.g. attractiveness, strength, intelligence)
• Evolutionary explanation - Ohman

  • Experimental support for this theory of 'biological preparedness' came form Ohman who gave participants electric shocks at the same time that they saw pictures of either snakes, houses or human faces
  • It was easier to condition a fear response to the snakes than it was to either houses or human faces, suggesting an inherited biological predisposition to fear of snakes
• Evolutionary explanation treatment

  • Embryo manipulation to reduce the inheritance of physical disorders by using genetic material from three parents is in the early stages of research
  • In the future, will this approach also be taken to the 'treatment' of mental disorders that are shown to have a strong genetic basis to them?
• Brain abnormality as an explanation - schizophrenia

  Brown et al revealed - in post-mortem studies compared the brains of patients with schizophrenia against those of patients with affective disorder - that the brains of schizophrenics were 6% light and had:

  • Enlarged lateral ventricles
  • Significantly thinner para-hippocampal cortices

  Weinberger found - by doing MRI scans of twins who were identical but who were not concordant for schizophrenia - that there were differenced between the two groups in the prefrontal cortex and hippocampal volume
• Brain abnormality as an explanation - depression

  • Research has shown that patients with depression can show a smaller hippocampal volume than people not experiencing depression
  • What may be happening is that people with depression have experienced stress which has led to the release of cortisol. There is evidence that cortisol can destroy hippocampal cells. This would mean that these hippocampal cells can then not respond to stimulation in the way that they normally might. If so, this would reduce the effect of serotonin in the body.
• Brain abnormality explanation - depression - Sheline

  Sheline found in a study of elderly women whose depression was in remission that the hippocampus was smaller in these women than it was in other women of the same age
• Brain abnormality explanation - depression - treatments

  Drug therapy would be most likely, although in some cases surgery may be used e.g. in the case of brain tumours that are producing symptoms of disorders)
• Biochemical explanation nature/nurture

  • Suggests explanations in terms of nature. Chemical imbalance (increased/decreased levels of certain neurotransmitters) causes mental illnesses
  • However, this has been shown to be affected by drug use so nurture may play a role
• Genetic explanation nature/nurture

  • Genes may predispose individuals to mental illnesses such as phobias or depression
  • But there is never 100% concordance, environmental factors may act as a trigger - 'switch the gene on'
• Brain abnormality explanation nature/nurture

  • The symptoms of mental illness are explained in terms of natural differences in either the structure or function of certain brain regions
  • But damage could be caused by lifetime experiences (e.g. trauma or stress)
• Biochemical individual/situational

  Individual differences in brain chemical activity leads to behavioural differences (i.e. symptoms of mental illness)
• Genetic individual/situational

  Some individuals are more susceptible to mental illnesses if parents suffered from the same condition
• Brain abnormality individual/situational

  Some individuals may suffer from mental illness due to damage or malfunction to certain regions of the brain - e.g. smaller hippocampus in depressed patients
• Biochemical usefulness

  Beneficial in suggesting ways of treating mental disorders by restoring the normal levels of the neurotransmitters (e.g. SSRIs used effectively to treat depression)
• Genetic usefulness

  • Currently, it is difficult to change someone's genetics so there are limited practical applications (although therapy could be used in the future)
  • Genetic screening could be used to inform people of the risks before they decide to have children
• Brain abnormality usefulness

  • It would be difficult/impractical to change someone's brain structure
  • But it could lead to drug treatments to increase or decrease activity in certain regions or possible surgery to restore normal function
• Biochemical validity

  • Issues with the use of correlation evidence to support the theory (e.g. is high serotonin/low dopamine cause or the result of mental illness)
  • Cannot directly measure/observe the actions of these neurotransmitters
• Genetic validity

  • Difficult to impose controls when carrying out family studies (other extraneous variables such as environmental factors when growing up are difficult to control)
• Brain abnormality validity

  Difficult to identify the cause of the brain abnormality and whether this or some other factor is the reason for the mental illness