Cannabis and mental illness: is there a link?
Zerrin Atakan
Consultant psychiatrist, senior lecturer National Psychosis unitMbr />
South London and Maudsley trust.
Cannabis, the complex plant
What was covered in the lecture:
Cannabis
plant as a psychoactive plant
Major ingredients of cannabis and their effects
on humans
The effects of cannabis on mental health
Links with depression
and anxiety
Links with psychoses
The Cannabis plant:
The
hemp plant (cannabis sativa) has been cultivated as a multipurpose economic plant
for thousands of years
Some are grown for their fiber content, others for
their psychoactive properties
The plant is a lush, fast growing annual which
can reach maturity in 60 days indoors and around 120 days outdoors
There are
male and female plants and both contain psychoactive ingredients. But female flowers
have a higher amount of THC (the main psychoactive ingredient).
Cannabis as a psychoactive plant
Cannabis
sativa: grows in many regions of the world. It has 5 - 11 leaflets with serrated
margins.
A sticky resin covers the flowering tops and upper leaves
The
resin contains the active ingredients of the plant.
What is cannabis
It's a complex plant with over 60 compounds and 400 chemicals. Two major compounds of the plant are delta-9 Tetrahydrocannabinol (THC) and Cannabidol (CBD)
Tetrahydrocannabinol (THC)
| Name | part of plant | THC content (%) |
| Marijuana | Leaves, small stems | 1.0 - 3.0 |
| Sinsemillia | Sterile female flowers | 3.0 -6.0 |
| Ganja | Compressed sterile female flowers | 4.0 - 8.0 |
| Hashish | Cannabis resin | 10 - 15 |
| Cannabis oil | Alcoholic extract of resin | 20 - 60 |
Street resin often has much smaller quantities of THC, due to adulteration with other substances.
The effects of THC on humans
NB THC in isolation
Psychological effects
Effects
on mood:"high", feelings of intoxication, anxiety (decreased to severe),
alertness, depression, increased sociability, paranoia, psychotic symptoms
Effects on perception: Distortion of perception, changes in perception of time
and space, hallucinations with doses above 15 milligrams THC
Effects
on cognition:
Impaired divided attention
Reduced task accuracy
Temporary,
does related short term memory impairment
Mental arithmetic impairment
Alteration of associative processes
Where does cannabis go our body?
1988
- a specific cannabinold preceptor was found in the brain
1992 - a brain molecule
called "anandamide" was identified, the molecule is from a Sanskrit
word "anadna" meaning "bliss"
The endogenous cannabinoid
system has numerous interconnections with a variety of brain structures.
Endogenous Cannabinoids
Cannabinoid receptors have also been found in lower vertebrates, from fruit flies onwards. This phylogentic distribution suggests that the gene must have been present early in evolution, and its conservation implies that the receptor serves an important biological function.
Does it effect mental health
Link between cannabis and depression and anxiety states
Does
cannabis use in early teens lead to development of higher rates of depression
and anxiety in young adulthood?
Australian study of 1601 students followed
for 7 years show that::
Daily use: Over five fold increase in the odds of
reporting a state of depression and anxiety
Weekly or more frequent use: two
fold increase
Links between cannabis use and severe mental illness (psychoses)
Questions:
Does cannabis trigger an earlier onset of psychosis in predisposed people
Does cannabis exacerbate the psychotic symptoms generally?
Does cannabis use
worsen the outcome and progress of the illness?
Is there a causal link?
What is the existing evidence?
Biological
studies
Epidemiological studies
Clinical practice
Biological studies:
THC
increases the release of dopamine in the brain
Dopamine is already known to
be increased in patents with schizophrenia
THC leads to a further increase
of dopamine
Therefore cannabis may act as a risk factor for this disorder.
NB Tobacco also increases the levels of dopamine in the brain, by extension it is also a risk factor. Most cannabis users smoke with tobacco and schizophrenia sufferers generally smoke large amounts of tobacco.
Epidemiological studies
A
causal link: Swedish study (1969) of 50,000 Swedish conscripts followed up for
15 years showed an increased risk amongst those who smoked cannabis
Those
who were heavy users at age 18 were 6 times more likely to develop schizophrenia
over the next 15 years
Increased risk of those who have a genetic vulnerability
(ie someone else in the family suffers from severe mental illness)
A
recent reanalyzes of the Swedish study showed there is an associated risk of developing
schizophrenia consistent with a causal relation. This association is not explained
by the use of other drugs or personality traits
A Dutch study (2002): 7500
people followed for 3 years. Regular consumers were more likely to develop schizophrenia
1037
individuals followed up from birth in New Zealand 1037 children:
At age 11:
information on psychotic symptoms
At ages 15, 18: Their first drug use assessed
At age 28: their psychiatric symptoms assessed
The study found that people
who used cannabis by the age of 15 were four times as likely to show an increase
in schizophrenic symptoms at the age of 26
Cannabis use is not secondary to
a preexisting psychosis
2437
young people (14 - 24 years) with and without predisposition for psychosis were
followed up for four years
After adjustment for other factors:
The effect
of cannabis use was much stronger in those with a predisposition for psychosis
than those without (23.8%)
There is a dose relationship with increasing frequency
of cannabis use
Predisposition to psychosis did not significantly predict
cannabis use four years later, thus refuting the self medication hypothesis
Clinical practice
about
85% of in-patients in South London use it on a regular basis
Sudden relapse
is frequently observed during admissions
Yale medical school study: Patients
with schizophrenia were given injections of THC and exacerbation of symptoms were
observed
Incidence of schizophrenia has doubled in South London since the
1960's
Outcome studies> Those who continue to smoke are three times more
likely to develop a chronic illness
So why do so many patients smoke cannabis?
"Makes
me feel relaxed"
"Helps me feel better"
"It's a herb,
does you no harm"
Maybe one of the few means of obtaining pleasure
Belonging to a group of people
Cultural belief systems
Easy availability
cheap
Cannabidiol may answer:
Available
data on CBD is limited compared to THC
CBD has no psychotomimetic effect in
man, it doesn't give a "high"
CBD has anti anxiety effects in mankind
and animals
CBD has a profile similar to "atypical" anti psychotics
CBD is currently being tried as an anti psychotic in patients with schizophrenia
Cannabidiol / THC?
Cannabidiol
/ THC ratio is important
People who smoke cannabis would normally be unaware
of this ratio
As CBD doesn't make you feel stoned, but THC does, dealers prefer
to sell high THC cannabis such as skunk.
Links between cannabis and psychoses
Questions:
Does
cannabis trigger an earlier onset of psychosis in predisposed people? - Yes
Does cannabis exacerbate the symptoms generally> - Yes
Does cannabis use
worsen the outcome and progress the illness? - Yes
Is there a causal link?
- Possibly, in those who are vulnerable.
Conclusions:
No
single mechanism can explain the multitude of effects of the cannabis plant. Different
ingredients have different effects.
Our understanding of this complex plant
and the cannabiniod pharmacology is more advanced than it was 10 - 20 years ago
The endogenous cannabiniod system has numerous interconnections with a variety
of brain structures and interacts with a host of neurochemical systems
Is cannabis bad for mental health?
Yes
if you are:
Young (early teens)
- since the mid 80's among young people
cannabis is more common than tobacco
NB - was stated as a fact and not challenged. Most cannabis is smoked with tobacco in the UK.
- between 1999 and 2001 the number of 14 - 15 year olds who had tried cannabis
rose from 19% to 29% in boys and 18% to 25% in girls
- more easily available
- cigarette smoking is frowned upon (belief that cigarettes are more harmful)
Smoke regularly
Smoke strong cannabis - especially in the last 10 years
cannabis is a lot more potent ("skunk")
NB this claim was strongly refuted later in the conference
Have
a family history of severe mental disorder
Have predisposition to develop
a psychotic illness