Schizophrenia

DSM-5 diagnosis of SZ

• 1 positive symptom for atleast 3 months

• Holistic assessment of symptoms

• Takes into account various factors when diagnosing e.g personality disorders or functioning levels

ICD diagnosis of SZ

• 2+ negative symptoms for atleast a month 

• Reductionist assessment of symptoms

• First rank symptoms (a specific list of symptoms for SZ only)

Negative symptoms of SZ definition

A loss of usual abilities and experiences

Negative symptoms of SZ examples

• Alovition = reduced drive/motivation, lack of energy

• Alogia/speech poverty = reduced quality/amount of speech, delayed verbal responses

• Disorganized speech = incohherent, slurring, change topic mid sentence, stop talking completely

Positive symptoms of SZ defintion

Additional experiences beyond those of ordinary existence

Positive symptoms of SZ examples

• Hallucinations = unusual sensory experiences (can relate to any sense but auditory/visual are the most common)

• Delusions/paranoia = false/irrational beliefs not based in reality (believing one is an important historical/religious figure is common)

• Disorganized speech = speak out stream of thoughts, slur/talk quickly (links to dopamine hypothesis) 

• Disorganized behaviour = strange, unpredictable actions that interfere w/ daily functioning

Inter-rater reliability of SZ

• Extent to which 2 assessors agree on the same diagnosis (independently)

• Symptoms of SZ in the same patient may be interpreted differently

• Lack of clarity between ICD/DSM

Study had 2 psychiatrists diagnose 100 patients using ICD/DSM:

• Psy 1 DSM = 26, ICD = 44

• Psy 2 DSM = 13, ICD = 24

Test re-test reliability of SZ

• Whether tests used to diagnose SZ are consistent overtime

• 37% concordance rate in test re-test diagnosis of SZ

• Bc symptoms are inconsistent & patients present differently

Predictive validity of SZ 

• Diagnosis leads to successfull treatment = valid

• SZ = low predictive validity

• Only 10% of SZ patients achieve significant, lasting improvements = recovery differs a lot

Descriptive validity of SZ

• Patients diagnosed w/ diff disorders should have diff symptoms

• SZ = low descriptive validity

• SZ has a huge symptom overlap w/ disorders like depression & bipolar

• Some patients show symptom of SZ but don’t meet diagnostic criteria

Aetiological validity of SZ

• All patients w the same disorder should have same cause to be valid

• SZ = low aetiological validity

• Aetiologically heterogenous = no one cause

SZ co-morbidity issues

• when 2 or more conditions occur tgt

• Study = ½ patients w SZ also had depression/substance abuse

• Confusing diagnosis bc patient may have severe depression and be diagnosed w SZ or vice versa

SZ gender bias issues

• since 1980s, men = more likely to be diagnosed w SZ (significantly) 

• Bc men = more likely to have an emotional outburst/breakdown compared to women 

• Maybe bc men are raised to not be emotional (stereotypical)

• Women typically function better = missed symptoms = suffer 4 life bc couldn’t be diagnosed 

SZ cultural bias issues

• ppl w african origin = more likely to be diagnosed w SZ

• Bc talking to ancestors can be classed as a positive symptom = misdiagnosis

Rosenhan SZ study

• 8 ppl w/ no history of mental illness

• Go to hospital and report only 1 symptom = hearing voices = all diagnosed w SZ (didn’t report more symptoms)

• Admitted & kept for avg 19 days before getting discharged

Follow up:

• Sent almost 200 genuine patients

• Quite a few staff and psychiatrists rated real patients as fake

Shows how the diagnosis of SZ is unreliable and invalid

Biological explanation of SZ

• Polygenetic = many candidate genes can cause SZ

• Aetiologically heterogenous = diff combos of diff genes can cause SZ

• Candidate genes = COMT & DRD4

Gottesman et al (1990s)

• large scale family study 

• MZ twins = 48% concordance rate 

• DZ twins = 17% concordance rate

• Both parents had SZ = 46% chance of SZ in kid 

•  1 parent had SZ = 16% chance of SZ in kid

Ripke et al (2014)

• Meta-analysis of 37k SZ patients 

• 108 diff genetic variations linked w increased risk of SZ

• Includes many genes which code for dopamine functioning

COMT & DRD4 genes

• Associated w/ excess dopamine in specific receptors

• Causes positive symptoms

Bio explanation strengths (