Download Cannabis and Psychosis

Filippo Passetti
16th April 2013
 Is
cannabis
dangerous?
 Is
it a gateway drug?
 Can
it cause
dependence?
 How
much is too
much?
 How
do you stop?
 Should
cannabis be
legalised?
1. Can cannabis cause acute psychosis?
2. Does it cause schizophrenia?
3. Does it worsen the course of
schizophrenia?
 Panic
(22%)
 Psychotic symptoms
(15%)
 Anxiety, paranoia
and
depression in 21%
 Impairment
of
memory (6%)
 Paranoia (6%)
 Apathy (5%)
 Anxiety/ panic (2%)
 Constriction
of the
field of awareness
 Slowing of the
passage of time
 Impaired immediate
recall…fragmentation
of thought
 Mood disturbance
 Depreson/ Derealis
 Two
studies found
– at high doses –
visual and auditory
hallucinations
 Some blocked, some
enhanced by pretreatment with
haloperidol
1. Can cannabis cause acute psychosis?
yes
2. Does it cause schizophrenia?
3. Does it worsen the course of
schizophrenia?
1. Can cannabis cause acute psychosis?
yes
dose-related, toxic psychosis
? indistinguishable from scz ?
probably on the rise
1. Can cannabis cause acute psychosis?
2. Does it cause schizophrenia?
3. Does it worsen the course of
schizophrenia?
1.
X
Y
2.
Y
X
X
3.
Z
Y
4.
No relation
1.
X
Y
2.
Y
X
X
3.
Z
Y
4.
No relation
•
•
•
•
•
•
•
Strength
Consistency
Specificity
Temporality
Direction
Plausibility
1. Can cannabis cause acute psychosis?
yes
2. Does it cause schizophrenia?
yes
3. Does it worsen the course of
schizophrenia?
1. Can cannabis cause acute psychosis?
yes
2. Does it cause schizophrenia?
yes
dose and age
not necessary or sufficient
not a v. big effect
possibly on the rise
1. Can cannabis cause acute psychosis?
2. Does it cause schizophrenia?
3. Does it worsen the course of
schizophrenia?
 24
CU vs 69 NCU SCZ patients
 At 1y:
> relapses/ exacerbations
earlier
even more in the heavier CU
(Linszen et al., 1994)
 24
CU vs 69 NCU SCZ patients
 At 1y:
> relapses/ exacerbations
earlier
even more in the heavier CU
(Linszen et al., 1994)
 24
CU vs 69 NCU SCZ patients
 At 1y:
> relapses/ exacerbations
earlier
even more in the heavier CU
(Linszen et al., 1994)
 96
R.O. SCZ, as NC/NC, C/NC, NC/C, C/C
 At 4y:
more continuous course in C/C
(Grech et al., 2005)
1. Can cannabis cause acute psychosis?
yes
2. Does it cause schizophrenia?
yes
3. Does it worsen the course of
schizophrenia?
yes
 Is
cannabis
dangerous?
 Is
it a gateway drug?
 Can
it cause
dependence?
 How
much is too
much?
 How
do you stop?
 Should
cannabis be
legalised?
General:
Castle D, Murray RM (2005). Marijuana and Madness. Cambridge, CUP.
1.
Casadio P, Fernandes C, et al. (2011). Cannabis use in young people: The risk for schizophrenia. Neurosci
Biobeh Rev 35:1779–1787.
2.
Caspari D (1999). Cannabis and schizophrenia: results of a follow-up study. Eur Arch Psych Clin Neurosci
249:45–49.
3.
Di Forti M, Iyegbe C et al. (2012). Confirmation that the AKT1 (rs2494732) Genotype Influences the Risk
of Psychosis in Cannabis Users. Biol Psych 72:811–816.
4.
Di Forti M, Morgan C et al (2009). High-potency cannabis and the risk of psychosis. BJPsych 195:488-491.
5.
Englund A, Morrison PD (2013). Cannabidiol inhibits THC-elicited paranoid symptoms and
hippocampal-dependent memory impairmentJ Psychopharmacol 27(1):19–27.
6.
Grech A,Van Os J, Jones PB et al (2005). Cannabis use and outcome of recent onset psychosis. Eur Psych
20:349–353.
7.
Kuepper R, Morrison PD et al (2010). Does dopamine mediate the psychosis-inducing effects of
cannabis? A review and integration of findings across disciplines. Schizophrenia Res 121:107–117
8.
Yucel M, Bora E,et al. (2012). The Impact of Cannabis Use on Cognitive Functioning in Patients With
Schizophrenia: A Meta-analysis of Existing Findings and New Data in a First-Episode Sample.
Schizophrenia Bulletin 38( 2): 316–330.