Biological Explanations of Schizophrenia

True or False: It has been observed that Sz runs in families.

What is the possible biological reasons that Sz seems to run in families?

Family research A [blank_start]meta-analysis[blank_end] of [blank_start]40[blank_end] families by [blank_start]Gottesmann[blank_end] showed that there was a clear relationship between the [blank_start]closeness[blank_end] (genetically) of the family member with Sz and the [blank_start]likelihood[blank_end] of developing the disorder. For the [blank_start]general population[blank_end] the chance of developing Sz is [blank_start]1[blank_end]%. If sombodies [blank_start]grandparent[blank_end] has Sz then the likely hood is [blank_start]5[blank_end]%. For a [blank_start]sibling[blank_end] it is [blank_start]9[blank_end]%, however he found for [blank_start]dizygotic[blank_end] (two egg) twins the likely hood was [blank_start]17[blank_end]% and for [blank_start]monozygotic[blank_end] it was [blank_start]48[blank_end]%. If [blank_start]one[blank_end] parent has sz then the chance is [blank_start]13[blank_end]% and if [blank_start]both[blank_end] parents have it then it goes up to [blank_start]46[blank_end]%. This suggests that there may be a [blank_start]genetic[blank_end] explanation as there may be an [blank_start]inherited[blank_end] sz gene that causes Sz. However the issue with family studies is that families share [blank_start]environments[blank_end] as well as genes therefore the results of this meta-analysis could be due to [blank_start]environmental[blank_end] and social factors rather than genetic.

Twin Study [blank_start]Gottesmann[blank_end] and [blank_start]Shields[blank_end] looked at the concordance rate for sz in [blank_start]24[blank_end] pairs of monozygotic and [blank_start]33[blank_end] dizygotic twins, from data that spanned [blank_start]26[blank_end] years. They found the concordance rate for dizygotic twins was [blank_start]9[blank_end]% and for monozygotic it was [blank_start]42[blank_end]%. As the MZ twins had a simnifically higher concordance rate it suggests that there may be a genetic factor, as they share [blank_start]100[blank_end]% of their DNA. However as they have identical genetic make up the concordance rate should be 100% but as it is only [blank_start]42[blank_end]% it suggests there may be other factors involved, such as environmental or social factors. The best way to study the effects would be to investigate twins that were reared [blank_start]apart[blank_end] which [blank_start]Gottesmann[blank_end] and [blank_start]Shields[blank_end] did in a later study. In a study of [blank_start]12[blank_end] twin pairs, [blank_start]7[blank_end] of whom were raised apart, they found a [blank_start]58[blank_end]% concordance rate which supports the genetic theory as most of them have not shared the same environment.

Which statement is true about the Stress Diathesis Model?

Which of these things does the Biochemical Explanation of Sz look at?

What is the Dopamine Hypothesis?

What can cause heightened dopamine activity at certain synaptic sites?

True or False: Modern research suggests schizophrenics have an abnormal dopamine D1:D2 receptor ratio.

Anti-psychotic Drug Research Anti-psychotic drugs are designed to [blank_start]block[blank_end] dopamine [blank_start]receptors[blank_end] in order to prevent them from being [blank_start]stimulated[blank_end] by the [blank_start]dopamine[blank_end], and therefore [blank_start]reduce[blank_end] symptoms of Sz. As the drugs have been proven to be effective it shows that there is a [blank_start]link[blank_end] between [blank_start]dopamine[blank_end] and the [blank_start]symptoms[blank_end] of sz, which supports the dopamine hypothesis. However the drugs only reduced [blank_start]positive[blank_end] symptoms, such as hallucinations, and was not [blank_start]effective[blank_end] for everyone. This suggests that the cause of Sz and its symptoms may be more [blank_start]complex[blank_end] than simply [blank_start]excessive[blank_end] dopamine activity, there could be other [blank_start]factors[blank_end] involved such as social or neuroatomical factors.

What is L-dopa?

True or False: L-dopa lowers dopamine activity.

Side effects of the drug [blank_start]L-dopa[blank_end], which [blank_start]raises[blank_end] dopamine activity, have included [blank_start]schizophrenia[blank_end]-like symptoms such as [blank_start]hallucinations[blank_end]. This side effect clearly displays the link between dopamine and the [blank_start]positive[blank_end] symptoms of sz which supports the [blank_start]dopamine[blank_end] hypothesis. However as L-dopa only produces [blank_start]positive[blank_end] symptoms of sz it suggests that there may be more to dopamine, it also suggest that the dopamine hypothesis is not a complete explanation of sz as it [blank_start]fails[blank_end] to explain the presence of [blank_start]negative[blank_end] symptoms.

What do Amphetamines do?

It was found that amphetamines...

Post Mortem Research Post mortem examinations of the [blank_start]brains[blank_end] of schizophrenic individuals found that schizophrenics had an [blank_start]increased[blank_end] number of dopamine [blank_start]receptors[blank_end] in specific parts of the brain ([blank_start]caudate[blank_end] nucleus [blank_start]putamen[blank_end]) compared to the number of [blank_start]dopamine[blank_end] receptors found in a non-schizophenic brain. This abnormal amount of dopamine receptors could explain the [blank_start]heightened[blank_end] dopamine activity and over-[blank_start]sensitivity[blank_end] to dopamine, which may be the cause of schizophrenic symptoms. However it is unclear whether these dopamine receptors were a [blank_start]cause[blank_end] or a [blank_start]consequence[blank_end] of sz, or whether it was a [blank_start]side[blank_end] effect of taking [blank_start]anti[blank_end]-[blank_start]psychotic[blank_end] drugs.

What did PET scans on schizophrenic individuals reveal?

What is the neuroatomical explanation for sz?

What neuroatomical differences did Brown find in his MRI research on the brain structure of schizophrenics?

Neuroatomical Twin Studies [blank_start]Suddath[blank_end] conduced [blank_start]MRI[blank_end] scans on [blank_start]monozygotic[blank_end] twins, one of them had sz and the other did not. He found that the sz twin had increased brain [blank_start]verticals[blank_end] and reduced brain [blank_start]weight[blank_end] compared to the non-schizophrenic twin. The brains of the twins, as they are [blank_start]monozygotic[blank_end], should have been identical as their genetic make up is identical however as the schizophrenic twin had a different brain anatomy it shows that there is a clear [blank_start]link[blank_end] between the abnormal brain structure and sz. However the cause and effect is unclear as they cannot tell if the structural abnormalities were a cause or [blank_start]consequence[blank_end] of sz.

Schizophrenia frontal lobe and pre-frontal cortex research Research has found that schizophrenics have [blank_start]reduced[blank_end] blood flow to the [blank_start]frontal[blank_end] lobe and reduced activity in the [blank_start]pre[blank_end]-[blank_start]frontal[blank_end] cortex when performing [blank_start]working[blank_end] memory tasks. The prefrontal [blank_start]cortex[blank_end] and frontal lobes are areas or the brain that have been associated with [blank_start]emotional[blank_end] response, impulse control and planning. A malfunction in these areas could explain the [blank_start]negative[blank_end] symptoms such as [blank_start]avolition[blank_end], the inability to persist in any goal orientated behaviour, and [blank_start]flattening[blank_end], a reduction in range and intensity of emotion, as they are linked to those areas of the brain. This is supported by the fact these brain anomalies have been primarily found in individuals who display predominantly [blank_start]negative[blank_end] symptoms, which suggests a link between an abnormal neural anatomy and the [blank_start]negative[blank_end] symptoms of sz; however, does not explain the presence of [blank_start]positive[blank_end] symptoms which suggest sz may be more complex that simply an anatomical difference int the brain.

True or False: Research has found that a disproportionately large number of schizophrenics are born in winter or early spring.

Which trimester of pregnancy is key for neural development

Neurodevelopmental Explanation [blank_start]Mednick[blank_end] investigated the incidents among the children of women who contracted a certain strand of [blank_start]influenza[blank_end] during a 5 week epidemic in [blank_start]Helsinki[blank_end]. [blank_start]Medick[blank_end] discovered that a significantly [blank_start]larger[blank_end] amount of children who were exposed to the infection during the [blank_start]second[blank_end] trimester, which is vital for [blank_start]neurological[blank_end] development, developed schizophrenia compared to those who were exposed to it in the first or third trimester. This is an attractive theory as it offers an explanation how individuals with no [blank_start]family[blank_end] history of sz [blank_start]suddenly[blank_end] develop it or why sometimes only one out of a pair of [blank_start]monozygotic[blank_end] twins develops it. However despite there being a [blank_start]positive[blank_end] correlation it is only a small [blank_start]positive[blank_end] correlation and not every child who was exposed to the influenza grew up to develop schizophrenia which suggests that the neurodevelopmental explanation of schizophrenia is too [blank_start]simplistic[blank_end] and that there may be other [blank_start]factors[blank_end] involved, such as social and environmental factors. A better explanation might be the [blank_start]stress[blank_end] [blank_start]diathesis[blank_end] model which is a [blank_start]combination[blank_end] of biological and psychological explanations. The biological factors, such as being exposed to the virus in the second trimester, may [blank_start]predispose[blank_end] and make the child vulnerable to developing sz; however, the psychological factors, such as high levels of expressed emotion at home, may [blank_start]trigger[blank_end] the schizophrenia to emerge and develop.