PSYC 412 Lecture 8: PSYC 412 Mar 28
14 May 2018
School
Department
Course
Professor
PSYC 412: Developmental Psychopathology
Mar 28th 2018
Lecture 21: Autism (cont.)
• Jim Carrey and Jenny McCarthy on vaccinations & autism
• Jenny McCarthy argues that toxins cause autism
• Environmental Factors: toxin hypothesis
o Vaccinations:
▪ There has been an increase in the # of vaccines children have
gotten over the last half century
▪ In 1900 you got one vaccine for smallpox
▪ In 1960 they added diphtheria, tetanus, pertussis and polio
▪ In 1980 the MMR (measles, mumps, rubella) and took away
smallpox vaccine (because nobody was getting it again)
▪ In 2000 included hepatitis, meningitis
o In Quebec: 14 separate shots by 6 years of age inc. pneumonia, flu,
Rhoda virus, chicken pox
o Principle concern around vaccines:
▪ Thimerosal (mercury)
• A preservative in vaccines
• They had removed nearly all thimerosal by that point except
for one flu vaccine given to adults
o Why did people think vaccinations were causing autism?
▪ We first start to see symptoms of autism occurring in the first two
years
▪ Right around the time that kids get their MMR vaccine
▪ Loose correlation: child gets shot, parents notice symptoms
▪ Also epidemiological data showing that increased use of MMR
vaccine coincided with increased prevalence of autism
• But in CA and Demark the increase in autism happened after
introduction of MMR vaccine
o Andrew Wakefield et al., 1998
▪ Published study in 12 children who had normal development
followed by onset of behavioral difficulties and gastrointestinal
problems
▪ For 8 of the children onset was linked to MMR vaccine by parents
or a physician
▪ The authors were careful to point out that this study didn’t prove link
between behavioral problems and vaccine
▪ Only a subset of autism cases after vaccination
o After publication, MMR vaccination rates dropped
▪ In the UK: 1996 was 92%, 2006, 85% (compared to 94% for other
vaccines)
▪ 2006 incidence rates for measles and mumps were 13 and 37x
higher than in 1997
o At this point, no credible evidence linking vaccines to the development of
autism
▪ 12 epidemiological studies found no link between MMR vaccine
and autism
▪ Largest study: all children born in Denmark between Jan 1991 and
Dec 1998 (N= 527, 303)
• Compared children who received MMR and who hadn’t
• Children in vaccinated group didn’t have greater risk of
developing autism compared to unvaccinated group
• No association between age of vaccination and autism
▪ 6 studies found no evidence of link between thimerosal and autism
▪ 3 studies found no evidence that thimerosal is associated with more
minor neurological difficulties
o More recently:
▪ De Stefano et al., 2013 in Journal of Pediatrics
• Association between level of immunological stimulation in
first two years of life (how many vaccines you’ve gotten) and
autism
• Found no association: greater number of vaccines was not
associated with developing autism
▪ Anti-vaccination group said that the problem with these studies is
that they were correlational, and we can’t really know that vaccines
are causing autism unless we do a study where we randomly
assign some people to get vaccines and some to not
• Funded study involving randomly assigning monkeys to
receive different types of vaccines
• Gadad et al., 2015 Proceedings of the National Academy of
Sciences
o 79 rhesus macaques randomly assigned to receive
▪ 1990s pediatric vaccination schedule
▪ 1990s schedule but 4x faster (they develop
faster)
▪ 2008 expanded pediatric vaccination schedule
▪ Only thimerosal containing vaccines
▪ Only MMR vaccine
▪ Control saline
o Found that vaccinations were not associated with
any behavioral changes
▪ E.g. stereotyped behaviors, fear-disturbed
behavior, positive social behaviors, non-social
exploring behaviors
▪ Vaccines not associated with any
neuropathological changes in the
cerebellum, hippocampus and amygdala
