Make your own free website on
          The Health Effects of Marijuana on Humans
                       by Marc Anderson
                        June 28, 1992
                       Psychology 101
    Marijuana has been used as a drug since the beginning of
time,  yet  there are still many mysteries about its  health
effects  on  humans.  Marijuana, or cannabis  sativa,  is  a
preparation  of the crushed flowers and buds of female  hemp
plant.   The  existence of the plant has  been  reported  as
early  as  1500-1200  BC. in China, and  cannabis  has  been
described as an analgesic as early as 200 AD (Walton, 1938).
Since then, an overwhelming number of studies have attempted
to   explain  the  physical  and  psychological  effects  of
cannabis on humans.
Physical Effects
    Physically,  cannabis is relatively  harmless.   Studies
have  observed interesting results, including that it causes
structural  changes  in  the  brain,  depresses  male  sperm
counts,   causes  chromosome  damage,  lowers   testosterone
levels,  and  damages  the lungs.   Most  of  these  claims,
however,  have  been  unreplicated in humans  or  have  been
contradicted by other work.  This section will address  each
of these reported negative side-effects.
   Various studies have claimed that cannabis destroys brain
cells  (Landfield et al., 1988; Haper et al.,  1977;  Meyers
and  Heath,  1979;  Heath et al., 1980).   However,  several
other  studies found no structural or neurochemical  atrophy
in  the  brain  at all (Cabral et al., 1991; Paule  et  al.,
1992;  Co  et  al., 1977; Kuehnle, 1977).   Furthermore,  it
should be noted that Heath's work was sharply criticized for
avoiding  safeguards  of bias and reporting  "changes"  that
occur  normally  in  the  mammalian brain  (Natl.  Acad.  of
Sciences, Inst. Medicine, 1982).
   Wu et al. (1988) found a correlation between cannabis use
and  low  sperm  counts in human males.  This is  misleading
because a decrease in sperm count has not been shown to have
a  negative effect on fertility and because the sperm  count
returns  to  normal after cannabis use has stopped.   (Natl.
Acad. Sciences, Inst. Medicine, 1982)
    Another  claim made was that cannabis causes  chromosome
breakage.  The primary source for this are studies that were
conducted  by  Dr. Gabriel Nahas in the early 1980s.   Nahas
observed abnormalities in somatic (not sex) cells of  rhesus
monkeys in vitro (i.e., in test tubes and petri dishes)  and
then  made  the  unjustified conclusion that  these  changes
would  occur in human bodies in vivo (in the body).   Nahas'
work  was  criticized by his colleagues  and,  in  1983,  he
backed away from his own conclusions.
    A  widely held claim has also been that cannabis  lowers
male  testosterone levels (Kolodny, 1974).  This theory  has
been  challenged by several studies (Block, 1991;  Mendelson
et   al.,  1974;  Coggins  et  al.,  1976)  that  found   no
correlation  at  all.   Marijuana and  Health  (Natl.  Acad.
Sciences,  Inst.  Medicine,  1982),  also,  after  reviewing
literature  at that time, concluded that "Due to conflicting
and  incomplete evidence, it is not possible to conclude  at
the present time whether marijuana smoking has a significant
effect upon gonadotropic and testosterone concentrations  in
    The most serious physical danger of using cannabis is in
smoking it.  Inhaling any sort of burnt plant matter is  not
very  good  for  the lungs.  Tashkin et al.  (1990)  reports
decreased  gas  exchange  capacity  and  the  existence   of
particle  residue in the lungs of marijuana smokers  several
times  greater than for tobacco smokers.  Wu et  al.  (1988)
noted that marijuana is several times more carcinogenic than
tobacco.   These findings, though, must be interpreted  with
caution.   In  both  studies,  smoked  marijuana   was   not
filtered,  while smoked tobacco was.  Tashkin et  al.  notes
that, "these differences could largely account for more than
twofold  greater tar yield from marijuana than tobacco  that
was measured using syringe-simulated puffs of similar volume
and  duration."  Smoking cannabis through a water-pipe  will
filter  out water soluble carcinogens and will also  greatly
cool  down  the smoke.  Furthermore, cannabis  need  not  be
smoked:   In Middle Eastern countries, it has been  consumed
through   teas   and  food  for  centuries,   avoiding   the
carcinogenicity of smoke altogether.
     Despite  cannabis'  known  negative  effects  to   lung
function,  it  has  never been reported to  cause  a  single
instance  of  lung cancer.  Tobacco, though, is expected  to
kill 400,000 people this year (Glenn, 1992).  If cannabis is
so much more dangerous to a user's lungs than tobacco and is
so  much  more  carcinogenic, why  aren't  there  stacks  of
reports  of  cannabis-induced lung cancer?  One  interesting
theory  is  that it's because tobacco tars are significantly
radioactive, while marijuana tars aren't at all.  Winters et
al.  (1982)  found  that a pack-and-a-half-a-day  smoker  of
tobacco  is exposed to 8000 mrem of radiation a year,  equal
to  the  dose  of  300 chest x-rays.  A  more  recent  study
indicates that a pack-and-a-half-a-day smoker receives 16000
mrem  of  radiation more than a non-smoker,  annually  (NCRP
Report  #95,  1987).  It could also be noted that  the  mere
contents   of  carcinogenic  chemicals  doesn't  necessarily
indicate  an  extreme health hazard.  For  example,  roasted
coffee  contains 800 volatile chemicals, of  which  only  21
have   been  tested  on  rodents,  and  of  those,  16  were
carcinogenic (Ames, 1990).  Coffee has never been considered
a great cancer-causing substance, though.
    Cannabis  has  also been known for its many  therapeutic
uses,  including  the  treatment  of  open  angle  glaucoma,
asthma, and the nausea associated with chemotherapy.  It has
also  been described as a tumor retardant, an antibiotic,  a
sleep-inducer, and a muscle relaxant (Cohen, 1980).
Psychological Effects
    The  psychological  effects of cannabis  use  have  been
described quite many years before the physical effects,  yet
are as accurate today as they were 100 years ago.  Following
is  an early account of its intoxicating properties made  by
Dr. John Bell in 1857:
           "I  had taken the drug with great skepticism
     as  to its reputed action, or at any rate with the
     opinion  that  it was grossly exaggerated,  and  I
     accordingly  made  up my mind not  to  be  'caught
     napping' in this way again, and to keep a  careful
     watch over my thoughts.  But while enforcing  this
     resolution  as I supposed, I found myself,  to  my
     own astonishment, waking from a reverie longer and
     more profound than any previous.  From skepticism,
     to  the  fullest belief of all I had read  on  the
     subject,  was  but  a step.  Its  effects  so  far
     surpassed anything which words can convey, that  I
     began  to  think  I was on the verge  of  narcotic
     poisoning; yet, strange to say, there was not  the
     slightest  feeling of inquietude on that  account.
     I  resolved to walk into the street.  While rising
     from the chair, another lucid interval showed that
     another  dream  had come and gone.  While  passing
     through  the door, I was aware of having  wandered
     again,  but how or when I had permitted myself  to
     fall into the reverie I was perfectly unconscious,
     and  knew  only that it seemed to have  lasted  an
     interminable length of time."  (Bell, 1857)
    The  user  of  cannabis feels the onset  of  the  "high"
between 7 seconds (when smoking) and up to 30 minutes (after
eating).    This  involves  a  relaxed  and  peaceful,   yet
sometimes  euphoric state of mind.  At high  doses,  it  can
cause  hallucinations.  The effects last from 2 to  4  hours
after  the drug is ingested, and it usually leaves the  user
in a relaxed state for several hours after the high.  One of
the  main intoxicating properties is that short term  memory
is  inhibited  for the duration of the high.   Thoughts  may
seem  unclear,  and  it might be difficult  for  a  user  to
concentrate    on    logical-complicated    concepts    like
   Long-term effects have been argued for many years.  There
are  claims of an "amotivational syndrome" where  users  are
said  to  withdraw  from  society  and  lose  ambition.   In
reviewing  evidence  for  and against  the  theory  of  this
"syndrome,"  however,  Marijuana  and  Health  (Nat.   Acad.
Sciences, Inst. Medicine, 1982) concluded that:
     "Such  symptoms have been known to  occur  in  the
     absence  of  marijuana.   Even  if  there  is   an
     association between this syndrome and the  use  of
     marijuana,  that  does  not prove  that  marijuana
     causes  the  syndrome.  Many troubled  individuals
     seek an 'escape' into use of drugs; thus, frequent
     use  of  marijuana may become one more in a series
     of  counterproductive behaviors for these  unhappy
Other  studies  have found another interesting  correlation:
Shedler   et  al.  (1990)  reported  these  results   in   a
longitudinal survey of adolescents:
     "Adolescents    who   engaged   in    some    drug
     experimentation  (primarily with  marijuana)  were
     the  best adjusted in the sample.  Adolescents who
     used  drugs  frequently were maladjusted,  showing
     distinct    personality   syndrome    marked    by
     interpersonal  alienation, poor  impulse  control,
     and manifest emotional distress.  Adolescents who,
     by  age  18, had never experimented with any  drug
     were  relatively anxious, emotionally constricted,
     and lacking in social skills."
Among other findings, Utah Power and Light spent $215.00 per
year  less on health insurance benefits for drug users  than
on  the control group, and employees who tested positive for
cannabis  at  Georgia Power Co. had a higher promotion  rate
than  the  company average, and were absent 30 percent  less
(Morris, 1991).
     Whether  cannabis  use  causes  permanent  physical  or
psychological changes in its users is still under  question.
The  most  serious concern is its effects on  the  pulmonary
system, yet, studies have often used poor controls (i.e., no
filtration)  and  their  results can  mislead  an  uncareful
reader.   Smoking  the  drug with a different  apparatus  or
ingesting it without smoking at all could greatly effect the
results of these studies.
    The  acute psychological effects of cannabis that  cause
its  intoxicating properties are no mystery, as any user can
report.   Long  term effects of cannabis use could  possibly
lead   to   the  so-called  "amotivational  syndrome,"   but
scientific evidence is lacking.
References Cited
Ames,   B.N.,  Gold,  L.S.   Too  many  rodent  carcinogens:
   Mitogenesis  increases mutagenesis.  Science.   Vol  149.
   Pg. 971.  1990.
Bell,  J.   On the haschisch or cannabis indica.  The Boston
   Medical  and Surgical Journal.  Vol LVI, No.  11.   April
   16, 1857.
Cabral,  G.  et al.  Chronic Marijuana Smoke Alters Alveolar
   Macrophage    Morphology    and    Protein    Expression.
   Fundamental and Applied Toxicolgy.  17:321-32.  1991.
Coggins,  W.J., Swenson, E.W., Dawson, W.W., et al.   Health
   status of chronic heavy cannabis users.  Ann. N.Y.  Acad.
   Sci.  282:148-161.  1976.
Co,  B.T.,  Goodwin, D.W., Gado, M., Mikhael, M., and  Hill,
   S.Y.   Absence  of  cerebral atrophy in chronic  cannabis
   users.  JAMA.  237:1229-1230.  1977.
Cohen,   S.    Therapeutic   Aspects.   Marijuana   Research
   Findings:  1980.  NIDA Research Mongraph 31.  1980.
Glenn, Reed.  Daily Camera.  Jan. 2, 1992.
Harper,  J.W.,  Heath,  R.G., and Myers,  W.A.   Effects  of
   cannabis  sativa  on ultrastructure  of  the  synapse  in
   monkey brain.  J. Neurosci. Res.  3:87-93.  1977.
Heath, R.G., Fitzjarrell, A.T., Garey, R.E., and Myers, W.A.
   Chronic  marihuana smoking:  Its effects on function  and
   structure  of  the  primate brain.  In  Nahas,  G.G.  and
   Paton,  W.D.M.  (eds)   Marihuana:   Biological  Effects.
   Analysis,  Metabolism, Cullarlar Responses,  Reproduction
   and Brain.  Pergamon Press:  Oxford.  1979.
Heath,  R.G.,  Fitzjarrell, A.T., Fontana, C.J., and  Garey,
   R.E.   Cannabis  sativa:  Effects on brain  function  and
   ultrastructure in Rhesus monkeys.  Biological  Pschiatry.
   15:657-690.  1980.
Kolodny,  R.C., Masters, W.H., Kolodner, R.M., and Toro,  G.
   Depression  of  plasma testosterone levels after  chronic
   intensive marijuana use.  NEJM.  290:872-874.  1974.
Kuehnle,  J., Mendelson, J.H., Davis, K.R., and New,  P.F.J.
   Computed   tomographic  examination  of  heavy  marijuana
   smokers.  JAMA.  237:1231-1232.  1977.
Landfield,   P.,   Cadwallader,  L.  B.,  and  Vinsant,   S.
   Quantitative  changes in hippocampal structure  following
   long-term   exposure   to   delta-9-tetrahydrocannabinol:
   possible  mediation  by  glucucorticoid  systems.   Brain
   Research.  Vol 443.  1988.
Mendelson, J.H., Kuehnle, J. Ellingboe, J., and Babor,  T.F.
   Plasma  testosterone  levels before,  during,  and  after
   chronic marihuana smoking.  NEJM.  291:1051-1055.  1974.
Morris, D.  Saint Paul Pioneer Press.  May 6, 1991.
National   Academy  of  Sciences,  Institute  of   Medicine.
   Marijuana   and   Health.    National   Academic   Press:
   Washington D.C.  1982.
NCRP  Report #95.  Radiation Exposure of the U.S. population
   from   consumer   products  and  miscellaneous   sources.
   National Council on Radiation Protection and Measurement.
   Dec 30, 1987.
Paule,  M.  et al.  Chronic marijuana smoke exposure in  the
   rhesus  monkey  II:   Effects on  progressive  ratio  and
   conditioned position responding.  Journal of Pharmacology
   and Experimental Therapeutics.  260:  210-22.  1992.
Shedler,   J.,   Block,   J.   Adolescent   drug   use   and
   psychological health:  A longitudinal inquiry.   American
   Psychologist.  Vol 45(5) 612-630.  1990.
Tashkin,  D.P., Fligiel S., Wu, T-C., Gong, H. Jr., Barbers,
   R.G., Coulson, A.H.,  Simmons, M.S., Beals, T.F.  Effects
   of  habitual use of marijuana and/or cocaine on the lung.
   Research Findings on Smoking of Abused Substances.   NIDA
   Monograph 99.  1990.
Walton,  R.P.  Marihuana:  America's New Drug Problem.  J.B.
   Lippincott:  Philadelphia.  1874.
Winters,  T.H.,  Franza,  J.R.  Radioactivity  in  Cigarette
   Smoke.  NEJM.  306(6): 364-365.  1982.
Wu,   T-C.,  Tashkin,  D.P.,  Djahed,  B.,  and  Rose,  J.E.
   Pulmonary  hazards of smoking marijuana as compared  with
   tobacco.  NEJM.  1988.