Posted by alexandra_k on September 27, 2006, at 21:16:49
In reply to Re: genetics of schizophrenia » alexandra_k, posted by SLS on September 27, 2006, at 18:07:50
hellos :-)
> a pair of identical twins do not have to be identical phenotypes due to the epigenetic differences in gene activity.
what is an 'epigenetic difference' if it is not the differential effect of the environment on how allels express in phenotype?
> I have a feeling that we need to better define what we mean by schizophrenia.
Current definition is:
A. Characteristic symptoms: Two (or more) of the following, each present for a significant portion of time [I wonder how much a 'significant portion' is?] during a 1-month period (or less if successfully treated):
(1) delusions
(2) hallucinations
[it is interesting that the way DSM defines hallucination makes hallucinations a subset of delusions, hence if you have (2) you will meet (1) for free]
(3) disorganized speech (e.g., frequent [whatever that means] derailment or incoherence)
(4) grossly disorganised or catatonic behaviour
(5) negative symptoms, e.g., affective flattening, alogia, or avolitionNOTE: Only one Criterion A symptom is required if delusions are bizarre or hallucinations consist of a voice keeping up a running commentary on the person's behaviour or thoughts, or two or more voices conversing with each other.
B. SOCIAL / OCCUPATIONAL DYSFUNCTION: For a significant portion of the time [?] since the onset of the disturbance, one or more major areas of functioning such as work, interpersonal relations, or self-care are markedly [?] below the level achieved prior to the onset (or when the onset is in childhood or adolescence, failure to achieve expected level of interpersonal, academic, or occupational achievement).
C. DURATION: Continuous signs of the disturbance persist for at least 6 months. This 6 month period must include at least 1 month of symptoms (or less if successfully treated) that meet Criterion A (i.e., active-phase symptoms) and may include periods of prodromal or residual symptoms. During these prodromal or residual periods, the signs of the disturbance may be manifested by only negative symptoms or two or more symptoms listed in Criterion A present in an attenuated form (e.g., odd beliefs, unusual perceptual experiences).
D. SCHIZOAFFECTIVE AND MOOD DISORDER EXCLUSION: Schizoaffective Disorder and Mood Disorder With Psychotic Features have been ruled out because either (1) no Major Depressive, Manic, or Mixed Episodes have occured concurrently with the active-phase symptoms; or (2) if mood episodes have occured during active-phase symptoms, their total duration has been brief relative to the duration of the active and residual periods.
E. SUBSTANCE / GENERAL MEDICAL CONDITION EXCLUSION: The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition.
F. RELATIONSHIP TO A PERVASIVE DEVELOPMENTAL DISORDER: If there is a history of Autistic Disorder or another Pervasive Developmental Disorder, the additional diagnosis of Schizophrenia is made only if prominent delusions of hallucinations are present for at least a month (or less if successfully treated).
Then there are some subtypes...
PARANOID TYPE:
A. Preoccupation with one or more deluisons or frequent auditory hallucinations.
B. None of the following is prominent: disorganized speech, disorrganized or catatonic behaviour, or flat or inappropriate affect.DISORGANISED TYPE:
A. All of the following are prominent:
(1) disorganised speech
(2) disorganised behaviour
(3) flat or inappropriate affect
B. The criteria are not met for Catatonic Type.CATATONIC TYPE:
clinical picture dominated by at least two of the following:
(1) motoric immobility as evidenced by catalepsy (including waxy inflexibility) or stupor
(2) excessive motor activity (that is apparantly purposeless and not influenced by external stimuli)
(3) extreme negativism (an apparantly motiveless resistence to all instructions or maintenence of a rigid posture against attempts to be moved) or mutism
(4) peculiarities of volountary movement as evidenced by posturing (volountary assumption of inappropriate or bizzare postures), stereotyped movements, prominent mannerisms, or prominent grimacing.
(5) echolalia or echopraxiaand there is residual type and there are different courses (episodic, continuous, partial remission etc etc)
What a mess...
I wonder if the subtypes are natural kinds? I think (though I could be wrong) that disorganised and catatonic subtypes tend to be more associated with structural abnormalities. I wonder if these are the types that tend to have the relevant gene too?
Dunno...
Different clinicians probably have a different threshold for how willing they are to dx Schizophrenia. Because of terms like 'usually' 'significant portion' and 'markedly' there could be variation between clinicians. I think that is what 'inter-rater reliability' is supposed to measure (how much clinicians judgements agree). But then there are problems with clinicians making dx's for insurance purposes and / or in order to authorise a certain medication...
poster:alexandra_k
thread:689461
URL: http://www.dr-bob.org/babble/20060927/msgs/689729.html