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SCHIZOPHRENIA, KEY DRUGS, :red_cross:Joseph reviewed 6 recent twin studies…
SCHIZOPHRENIA
GENETICS
Chromosome 22
Found that some Sz P have small deletion in 22q11 - region of Chromosome 22
22q11 : contains several genes which are thought to increase risk of Sz [loss to 1 or more of these genes may affect brain in ways which increase Sz risk]
:red_cross: However relationship between these gene losses and the subsequent development of Sz isn't well understood
22q11.2 deletion syndrome - most people with this are missing about 3 million base pairs on 1 copy of chromosome 22 in each cell
--> The deletion occurs near the middle of the chromosome at a location designated as q11.2 - that region contains 30-40 genes
Prevalence of 22q11.2 is 10-20 times higher in Sz P than general pop
Genetics has an impact on risk of developing Sz :
- General pop = less than 1%
- 1st degree relative = 6-17%
- 2nd degree relative = 2-6%
- MZ twin = 48%
:red_cross: Research has failed to isolate a single recessive or dominant gene which seems to cause the illness [Tamminga & Schulz 1991]
Many researchers believe Sz is result from expression of multiple genes rather than a single gene eg : [Harrison & Owen] suggested up to 6 different genes which may be involved in susceptibility of Sz
Harrison et al - argues that the causative influence of genes on Sz which may be the result of genes' effect on the functions of synapses & circuitry in the brain
:red_cross: Would expect 100% concordance rate for MZ as they share 100% DNA [40-50%] --> Sz must be due to multiple factors incl genetics but not solely genetics
Family&Twin Studies
Gottesman [1991] meta-analysis :
- DZ twins = 17%
- MZ twins = 48%
- Other siblings = 9%
--> results show genes must have impact on dev of Sz and MZ twins have higher rate of dev than DZ
--> accountable for higher risk of birth complications for twins & MZ twins more likely to experience identity confusion compared to DZ twins or siblings [Joseph]
--> difficulty seperating nat from nurt
Gottesman [91]
- Risk of dev Sz [dual Sz parents] = 46%
- Risk of dev Sz [one Sz parent] =17%
--> Supports genetic expln but must not be the only cause for dev Sz
Kety : Found Sz was diagnosed in 16% [high risk gr] compared to 1.9% [low risk gr]
& Schizotypal PD diagnosed in 19% [high risk gr] compared to 5% [low risk gr]
--> overall High risk gr = 35% with disorder
compared to Low risk gr = 6% with disorder
Fischer : found that the discordant MZ twin [who didn't dev Sz] is likely to pass on vulnerability to child [9.4% compared to 12.3%]
Adoption Studies
Heston : Found 10.6% of adopted children w/ Sz mother also dev Sz compared to 0% from controls [healthy bio mother]
Tienari : 155 children [bio sz mum] vs 155 children [bio non Sz mum]
Found 10.3% dev Sz [Sz mum] compared to 1.1% [non Sz mum]
So provides evidence that there is partly a genetic aspect to dev of Sz
however doesn't explain why children without Sz mothers, dev Sz --> must be other causes
May be high stress levels in adoptive family/ big life events = act as trigger [stress-diathesis model]
TREATMENTS
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Family therapy
Psychoeducation = enables family to better understand the illness [prevelance, treatment, role of NT, side effects of drugs, symp]
Having a support system within the family can be beneficial for Sz P as those closest to them are educated on the MHD. Can identify triggers and know how to deal with them
:red_cross:
- time consuming [3-12 months]
- expensive
- family must be willing to engage
- not much effect by itself
:check: Pharoah [meta analysis 53 studies]
Found Fam therapy more effective in conjunction w/ drugs
Fam therapy increases compliance to Sz med
Reduced relapse rate
:check: Anderson et al : Found relapse rate was less than 5% when drugs & fam management used in conjunction
on its own : [drugs =40%] or [fam man = 20%]
COGNITIVE
Frith : Sz P have hi "self awareness" where they cannot filter out cognitive noise --> causing +ve symp due to lack of self monitoring
:check:Johns et al Found that the ppts w/ Sz [verbal hallucinations or delusions] were more likely to misattribute the source of the voice when presented with own voice which had been distorted [more common for p w/ hallucinations]
--> Sz P have problems detecting own voice
--> may be significant for p w/ hallucinations
:check: McGuigan found the voice box of Sz P was often active during the time they claimed to be experiencing auditory hallucinations [mistaking own voice for someone elses]
:check:McGuigan et al - found Sz P have less activity in parts of temporal lobe [involved in inner speech] --> indiv may have mistaken an internal convo as someone elses voice
Theory of mind : cog skill to be able to read and interpret the intentions of other people's behav
Sz P lack theory of mind --> explaining their delusions & paranoid of other peoples intentions
:check:Drury et al - found Sz P have deficits in theory of mind
However may be due to info processing overload when faced w/ complex tasks --> may be due to impaired cog ability rather than deficit in theory of mind
:check:Corcoran et al - found Sz P have deficits in tasks requiring ToM --> strong evidence behind that Sz is a cog cause
:red_cross:Beck et al argues that low levels of dop to brain = struggle processing more info --> cog insufficiency [sets pathway to psychosis]
--> May be a pre-existing bio risk factor which affects cog abilities
--> Signif stressor in indiv life = decline in cog = dev Sz
--> expln must be rooted in bio
:red_cross:Sitskoom - cog deficits were also found in relative of Sz p --> must be a genetic component
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KEY DRUGS
Sertindole [atypical] - few neurological and metabolic side effects but can cause cardiac arrhythmia
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Clozapine [atypical] - low in neurological side effects - does have metabolic→[works for most people especially when there’s an overlap between positive and negative symptoms]
:red_cross:Joseph reviewed 6 recent twin studies & found less significant results than Gottesman : MZ = 22.4% compared to DZ = 4.6%
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Evaluation :
:check:McEvoy et al - Atypicals have higher adherence eg : Clozapine has highest adherence as it has fewer side effects
:red_cross:Lieberman et al - the side effects are a major reason why p stop taking medication
:red_cross: informed consent needs to be given from p but the sz p are not in the right frame of mind -->hospitals and family give consent