This is not an easy read, nor is it a fun read. However, if you are looking for statistics on the growth of autism in various countries it has a wealth of information. Great for grant writers...Once again, I can't recall where I came across this information but perhaps it will come in handy for someone.
Past Prevalence Studies of Autism
There have been numerous studies conducted in separate countries to determine how many children had autism spectrum disorders over the past 40 years.
Many of the studies found a substantial proportion of children had a physical condition such as maternal rubella, prenatal trauma, encephalitis, epilepsy or tuberous sclerosis which were all potential explanations for the autism disorders. Most of today's children with autism were born healthy and suffered no injury or illness that could be a possible explanation.
Different diagnostic criteria were used in the studies. Those used were:
Kanner's Criteria:
1) A profound lack of affective contact
2) Repetitive, ritualistic behavior which must be of an elaborate kind
*Kanner gave some examples of behavior and did not include age of onset as essential. Kanner's Criteria for diagnosis is the most restrictive criteria used. It mainly focuses on the most severe forms of autism and does not allow for milder cases of autism found in Asperger's Syndrome and PDDNOS (Pervasive Developmental Disorder Not Otherwise Specified). Some studies, however, that used Kanner's criteria allowed for "atypical" autism cases to be counted, or those that did not fully fit the picture of Kanner's criteria.
Rutter's Criteria:
1) Impaired social development which has a number of special characteristics out of keeping with the child's intellectual level
2) Delayed and deviant language development that also has certain defined features and is out of keeping with the child's intellectual level
3) "Insistence on sameness" as shown by stereotyped play patterns, abnormal preoccupations or resistance to change
4) Onset before 30 months
*Rutter gave many examples of behavior. Rutter's Criteria for diagnosis is broader than Kanner's and allows for more children to be diagnosed, but whom still fit more typical or classic autism patterns. Milder cases of the Autism Spectrum would still not fit the criteria.
DSM-III Criteria
1) Lack of responsiveness to others
2) Language absence or abnormalities
3) Resistance to change or attachment to objects
4) The absence of schizophrenic features
5) Onset before 30 months
*DSM-III also had categories for childhood onset (after 30 months and before 12 years) and for atypical pervasive developmental disorder (PDD).
*The DSM-III criteria for diagnosis was far broader than any previous criteria. It recognized that autism could occur in any level of severity and now included the symptoms of Asperger's Syndrome, although it did not directly name the disorder. Passive acceptance of social approaches and one-sided approaches were now included as social impairment. The criteria allowed for more milder cases of autism to be counted.
DSM-III Revised criteria:
1) Impairment in reciprocal social interaction (at least 2 from 5 items, comprising of specified clinical examples)
2) Impairment in verbal and nonverbal communication (at least 1 of 6 items)
3) Markedly restricted repertoire of activities and interests (at least 1 of 5 items)
4) A grand total of at least 8 from among the 16 items listed.
*This shift included children with the most subtle symptoms. The DSM-III Revised criteria for diagnosis was the broadest criteria to exist to date. The DSM-III had been revised because many doctors believed the DSM-III was too restrictive and did not allow for children who were clearly autistic to be diagnosed because of varying symptoms and histories. But, many doctors felt that the DSM-III Revised edition was too broad and would include children who did not have autism to fit the criteria. The various subtypes of the spectrum were put into a single category of PDDNOS.
Criteria used in one Japanese study:
1) Disturbed interpersonal relationships (defined by a list of clinical examples comprising of 9 items)
2) Absence or deviance in speech and language development (8 items).
3) Insistence on the preservation of sameness or resistance to change (6 items).
4) Abnormal responses to sensory stimuli or motility disturbance (10 items).
*The criteria used in this one study is a mix of new and old criteria used in other studies. Numbers 2 and 3 are similar to criteria used in other studies, but the broadness of number 1 is different than others and number 4 is the only criteria that included sensory and motor disturbances.
Today's criteria, DSM-IV:
DSM-IV, which is used today, continued the broader conception of the DSM-III, yet attempted to rein back on its DSM-III Revised edition by combining the two, but also restricting the criteria so that it would not catch those who did not have an autistic disorder. It achieved this by improving its specificity as well as separating the subtypes of autism.
Countries and Birth Years
COUNTRY STUDY YEAR BIRTH YEARS AGES PER 10,000 CRITERIA
Denmark 1972 1949 - 1960 2 to 14 4.3 Kanner's
Ireland 1984 1965 - 1968 8 to 10 4.3 similar to DSM-III
Canada 1988 1971 - 1979 6 to 14 10.1 DSM-III Revised
Germany 1986 ? - ? under 15 yrs 1.9 Rutter's
England 1966 1953 - 1955 8 to 10 4.5 Kanner's
England 1979 ? - ? 3 to 17 4.9 Kanner's
England 1970's 1956 - 1970 3 to 17 20 Researcher's Own
England 2001 ? - ? under 18 yrs 62.5 assumed DSM-IV
**Sweden 1983 1960 - 1979 0 to 20 5.6 Rutter's
Sweden 1984 1962 - 1976 4 to 18 4 DSM-III
**Sweden 1983 1964 - 1966 13 to 15 4.6 Rutter's
**Sweden 1983 1970 - 1972 7 to 9 12.6 Rutter's
*Sweden 1986 1975 - 1984 0 to 10 7.5 DSM-III
*Sweden 1991 1975 - 1984 4 to 13 11.5 DSM-III
Sweden 1993 ? - ? school aged 36 Unknown
France 1989 1966 - 1973 6 to 12 6.5 DSM-III
France 1992 1972 - 1976 16 to 20 4.9 France's Own
France 1989 1979 - 1983 5 to 9 10.8 Rutter's
Japan 1971 1968 - 1974 4 to 10 5 Kanner's
Japan 1983 1970 - 1976 6 to 12 16 (high) Japan's Own
Japan 1987 1971 - 1979 4 to 12 15.5 DSM-III
Japan 1988 1972 - 1978 annual age 7 13.8 DSM-III
Japan 1989 1979 - 1984 3 to 5 13 DSM-III
USA 1970 1962 - 1967 3 to 12 3.1 child schizophrenia
USA 1987 ? - ? 2 to 18 3.3 DSM-III
USA 1989 1975 - 1979 8 to 12 4 DSM-III
USA 1998 1988 - 1995 3 to 10 66.7 assumed DSM-IV
USA 2001? 1988 - 1995 3 to 10 68.5 assumed DSM-IV
USA Today's Rate 60.24 DSM-IV
Since it would not be unusual for different countries to have different rates of autism, it is important to evaluate the countries separately. This would be particularly true if an environmental factor is playing a role in causing autism in many cases. It was explained by some of the studies that immigrants from certain areas held higher rates of autism in their studies than native citizens.
In this case, it is important to look at each country separately to evaluate whether or not they themselves had increases in autism rates according to birth years and criteria used.
For some countries, we do not have several studies to compare. But, in others, we do.
In England, they had approximately the same rates using Kanner's criteria. In using their own broad criteria, they found many more they felt fit the picture of autism in some form. The criteria used was extremely broad and specifically searched for children with Asperger's and, still, it did not find as many children as was found in 2001.
In Sweden, it did not seem to matter if they used Rutter's criteria or the DSM-III. Children born before the 1970's held approximately the same rates. Those numbers rose, still using Rutter's criteria, during the 1970's. Those numbers stayed consistent through the 1980's as is shown in the study that continued from when children were too young to be diagnosed to the follow up study done in 1991. In 1993, they checked school-aged children for Asperger's only and found an increased rate.
In France, the only study that did not show as high a rate as when they used their own criteria. The DSM-III rate was even lower than the one using Rutter's, and the Rutter's was used for children born later from 1979 to 1983.
Japan consistently holds the highest rates overall found for autism. But, again, the rates only rise after 1970. This may or may not be interpreted as a criteria change.
The United States was consistently low until after 1988. The first study was highly criticized for only looking at children diagnosed with childhood schizophrenia and using case notes, but it is also noted that the rates found are similar to the other studies. Since the DSM-III was used for many, it is hard to say that the DSM-IV changed the rates that significantly since the DSM-III also included symptoms of Asperger's even if it did not specifically name it.
Year Of Birth By Criteria
Kanner's
COUNTRY STUDY YEAR BIRTH YEAR AGES PER 10,000
Denmark 1972 1949 - 1960 2 to 14 4.3
England 1966 1953 - 1955 8 to 10 4.5
England 1979 ? - ? 3 to 17 4.9
Japan 1971 1968 - 1974 4 to 10 5
Using criteria to evaluate changes in rates, Kanner's criteria does not change much, although it is rising ever so slightly, but the birth years also contain all children born before 1974.
Rutter's
COUNTRY STUDY YEAR BIRTH YEAR AGES PER 10,000
**Sweden 1983 1960 - 1979 0 to 20 5.6
**Sweden 1983 1964 - 1966 13 to 15 4.6
**Sweden 1983 1970 - 1972 7 to 9 12.6
Germany 1986 ? - ? under 15 1.9
France 1989 1979 - 1983 5 to 9 10.8
Using Rutter's criteria, the rates of autism are the same as Kanner's before the 1970's. The rates then change and go higher. The only one that stays low is Germany but we do not have specific birth years to know when these children were born.
DSM-III
*Similar to DSM-III
COUNTRY STUDY YEAR BIRTH YEAR AGES PER 10,000
Sweden 1984 1962 - 1976 4 to 18 4
*Ireland 1984 1965 - 1968 8 to 10 4.3
France 1989 1966 - 1973 6 to 12 6.5
Japan 1987 1971 - 1979 4 to 12 15.5
USA 1987 ? - ? 2 to 18 3.3
Japan 1988 1972 - 1978 annual 7 13.8
USA 1989 1975 - 1979 8 to 12 4
Sweden 1986 1975 - 1984 0 to 10 7.5
Japan 1989 1979 - 1984 3 to 5 13
Using the DSM-III criteria, the rates again stay low for children born before the 1970's. A slight rise is found in France with children who are born in the 1960's and early 70's. After the 1970's, the rates are consistently higher for all but the USA. Sweden's one study is also a bit lower but that is the one that had children too young to be diagnosed and were added in later.
DSM-III Revised
COUNTRY STUDY YEAR BIRTH YEAR AGES PER 10,000
Canada 1988 1971 - 1979 6 to 14 10.1
Sweden 1991 1975 - 1984 4 to 13 11.5
The DSM-III Revised is the broadest criteria ever to be established. Many doctors were concerned that it was so broad that it would capture children who were not autistic at all. Still the rates were similar to others in the 1970's and early 1980's.
Researchers in England, again, used their own criteria that was extremely broad and specifically searched for children who would fit Asperger's descriptions. They had one of the most thorough studies done and found children others had perhaps missed. But, their numbers for those born before 1970 were still far lower than today's rates.
Assumed to be DSM-IV
COUNTRY STUDY YEAR BIRTH YEAR AGES PER 10,000
Sweden 1993 ? - ? school aged 36
USA 1998 1988 - 1995 3 to 10 66.7
USA 2001? 1988 - 1995 3 to 10 68.5
UK 2001 ? - ? under 18 62.5
USA today's rate 60.24
The studies that are assumed to be using the DSM-IV criteria are significantly higher than other studies. However, they also have children that are all born after 1988.
Classic Autism
With the criteria argument looming, the best way to evaluate if autism rates are due to criteria changes or a true rise in cases is by checking classic Kanner's autism. The criteria changes were due to including the other subtypes of autism that some argue may have been missed before. Adding them in now would indicate a change in rates due to their being diagnosed.
However, classic autism has not changed. Classic autism does not include PDDNOS, Asperger's, or any other subtype. It is strictly classic autism as defined by Kanner.
COUNTRY STUDY YEAR BIRTH YEAR TOTAL CASES CLASSIC CRITERIA
Denmark 1972 1949 - 1960 4.3 Kanner's
England 1966 1953 - 1956 4.5 2 Kanner's
Japan 1971 ? - ? 5.02 assume Kanner's
England 1979 ? - ? 4.9 2 Kanner's
England 1970's 1956 - 1970 20 5 Researcher's Own
Sweden 1983 1960 - 1979 5.6 3 Rutter's
USA 1970 1962 - 1967 3.1 0.7 Child Schizophrenia
Sweden 1984 1962 - 1976 4 2 DSM-III
Sweden 1983 1964 - 1966 4.6 Rutter's
Ireland 1984 1965 - 1968 4.3 similar to DSM-III
France 1989 1966 - 1973 6.5 4.7 DSM-III
Japan 1982 1968 - 1974 5 Kanner's
Sweden 1983 1970 - 1972 12.6 Rutter's
Germany 1986 ? - ? 1.9 Rutter's
Japan 1983 1970 - 1976 16(high) Japan's Own
Japan 1987 1971 - 1979 15.5 15.5 DSM-III
Canada 1988 1971 - 1979 10.1 DSM-III Revised
France 1992 1972 - 1976 4.9 4.9 France's Own
Japan 1988 1972 - 1976 13.8 DSM-III
USA 1987 ? - ? 3.3 1.2 DSM-III
*Sweden 1986 1975 - 1984 7.5 4.7 DSM-III
*Sweden 1991 1975 - 1984 11.5 8.4 DSM-III Revised
France 1989 1979 - 1983 10.8 8 Rutter's
Japan 1989 1979 - 1984 13 DSM-III
USA 1989 1975 - 1979 4 DSM-III
USA 1998 1988 - 1995 66.7 40 assumed DSM-IV
USA 2001? 1988 - 1995 68.5 assumed DSM-IV
UK 2001 ? - ? 62.5 16.8 assumed DSM-IV
USA today's rate 60.24
Cases of classic autism do stay consistently low until children are added in that were born in the 1970's, and then we see a slight rise. Japan is the only country that shows a significant increase in classic autism. The USA is the only country that shows a very low number during those years, but it is also noted that we do not know the exact birth years in the study of 1987.
Cases of classic autism also show a that they about doubled again in studies with children born during the 1980's, but the numbers are still lower with the average being around 8 per 10,000.
Cases of classic autism rose by 5 fold for those born after 1988 in the USA and doubled for those in the U.K..
Cases of classic autism do not change according to criteria changes that included milder and higher functioning cases of autism.
Conclusion
From these studies, it is not difficult to see the rising numbers.
The M.I.N.D. Institute in California also concluded that autism is rising and cannot be accounted for by changes in criteria. They are the only researchers keeping an accurate count of all autism cases in their state and they are primarily counting classic autism cases.
The CDC has also confirmed that autism is rising and cannot be accounted for by criteria changes.
After evaluating these studies, we would have to agree.
AutismFACTS to Consider
Interestingly, these prevalence studies give us insight into the most recent studies conducted by the CDC, Denmark, Sweden and England that the IOM relied upon to state that there is no conclusive evidence that autism may be caused by Thimerosal exposure.
While those mentioned studies were not actual prevalence studies, but instead were looking at what effect Thimerosal had on the increasing the numbers of autism, prevalence certainly was a basic part of the studies.
In 1970, Treffert did a study on the prevalence of autism in Wisconsin, USA. He was criticized for only using computer printouts as information for his study. In 1989, Aussilloux used only case notes for his study. In 1992, Fombonne and du Mazaubran used case notes only during their study. Using computer printouts or case notes only are not a preferable method for counting cases of autism, particularly combined with the absence of doing actual interviews and examinations.
All of the above studies used only computer data to count and to evaluate children with diagnosed autism. So did the CDC Thimerosal study and the other three.
Treffert was also criticized because he looked at computer printouts of cases of "childhood schizophrenia" and then attempted to diagnose how many were actually autistic. It is unknown how many cases were actually autism or another type of mental disorder.
The CDC Thimerosal study used children that were diagnosed with other disorders and admit that some were too young to be diagnosed with autism. Further, they only used the first diagnosis a child ever received and discounted any diagnosis that followed. It is unknown how many children were lost from the study who actually had autism.
In 1986, a study done by Steinhausen in West Berlin, Germany was criticized for only using two locations for their information. They used a clinic for child psychiatry and a center providing a program for autistic children. This limited the study substantially by restricting the various locations an autistic child could be found, the number of children studied, and does not allow for random choice which is pivotal for any statistical or population study.Most of the other studies used numerous locations sources such as schools, clinics, and so on.
The CDC Thimerosal study used 2 HMOs and they even limited which clinics the HMOs served in the study, cutting some out that carried high risk numbers. Both HMOs were under the same corporation but in two separate locations. A third HMO added after the initial studies was bankrupt, taken over by the state, and was noted for their incompetent record keeping.
Almost all of the previous prevalence studies searched for children who were diagnosed and undiagnosed in order to get a true record of exactly how many children had an autism spectrum disorder.
The CDC Thimerosal studies only used the actual diagnosed cases for their evaluations and only if they were diagnosed with autism before anything else.
The CDC Thimerosal studies only used the actual diagnosed cases for their evaluations and only if they were diagnosed with autism before anything else.
The various studies done in the past studied children whose average age began at age 5.25 years. The average age for the end of study was 13 years old. The actual ages ranged in each study, from 0 to age 10, but the Swedish studies that began at age 0 followed up to see if each child eventually became diagnosed in later years. They also broke down the other study to show the rate of autism in older children separately.
The CDC study examined the computer data on children from 0 to under 5 years of age. They did follow up but the 0 year olds would still have been under the age of 2 at that point, and they were still only counting the first diagnosis a child received and disregarding any that followed.
Most of these previously conducted studies had a high proportion of children with known possible causes of their autism.
The four studies done by the CDC, Denmark, Sweden and England had no possible explanations for what caused the autism.
While the actual prevalence studies done by the CDC in 1998 showed a prevalence of 66.6 per 10,000, their Thimerosal study produced a prevalence of only less than 1 per 10,000.
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