Autism and Gastrointestinal Disorders – Pediatrics study pt. 1
As promised, I am going to talk about the new report on autism spectral disorders (ASDs) and gastrointestinal (GI) disorders published in the January 2010 issue of the journal Pediatrics. To see the original report, click here. Also a disclaimer, again, this site is for discussion of scientific studies ONLY. I am a scientist, not a physician, I am NOT giving medical advise. If you or someone in your family have a health issue, please discuss it with your doctor.
For this study, a team of 28 physicians and academic researchers, all experts in fields related to pediatrics, ASDs and / or GI disorders, reviewed the current scientific literature on ASDs and GI disorders. The text does not say exactly how many studies were reviewed, but the citations list 82 papers. Each paper was assigned to two of the study participants, and each participant was asked to read the study, summarize its findings and judge the quality of the study based on criteria such as number of study participants, presence of proper controls, etc. Participants then spent two days at a conference in Boston discussing these studies and coming up with 23 consensus statements, things they could all agree were true. I’m going to go through the study and pull out these statements, quoting them in italics and then offering an explanation.
At the beginning of the report, the committee said,
“Because of the absence, in general, of high-quality clinical research data, evidence-based recommendations are not possible at the present time. However, the panel agreed on a number of statements based on expert opinion that arose from a review of existing evidence. It is acknowledged that, in many areas, evidence is generally confined to case reports, observational or descriptive studies, and poorly controlled or uncontrolled studies.”
Basically what the committee is saying here is that there is not a lot of what they would consider well done studies out there. Most of the evidence that they have comes from:
1) case reports — doctors, psychiatrists, or other professionals writing up a report on an individual patient. This is the kind of evidence Ms. McCarthy is talking about in the ABC News clip I linked to in “Shame on You ABC News!” It’s often called anecdotal evidence because its comes from a person telling their life story. These case reports include family history, medical information and stories told by family members to the person writing the report. These are a good starting point for scientific investigations, but they are difficult to draw strong conclusions from because they are only about one person, and what works for one person doesn’t always work for everybody. Plus, these reports are not always accurate. People leave things out, either because they don’t remember or are embarrassed to admit certain things; plus doctors and other professional have biases that affect what gets written in the reports as well. However, lots of case reports put together can be valuable because they allow researchers to look for trends and start asking questions in a more controlled way.
2) observational/descriptive studies — these are like the coffee and prostate cancer study I talked about earlier. People did what they would normally do in their lives without any input from an outside force. Researchers observe what happens and try to draw conclusions based on correlations they see. Again, these studies can be valuable starting point for research because they provide a lot of information. The more people involved and the longer the observation goes on, the more information it will provide. Unfortunately, many of the observational studies that have been done on ASD and GI disorders are on small groups for short periods of time. This makes scientists worry that they are missing valuable clues because the amount of information they have is very small and could be biased based on the same issues I talked about in the case studies section above (people leaving out information, researcher bias, etc).
3) poorly controlled or uncontrolled studies — an example of the type of controlled study the committee is talking about is a drug trial. A group of people are questioned about their health and then observed for a period of time, then given a medication for a period of time, observed and questioned again. Just like with the other studies, the more people participate in the study and the longer the study goes on, the stronger the conclusions will be. Studies like this also often involve controls, such as randomly splitting the participants into two groups and giving them either the medication or a treatment that does nothing (participants MUST be told before they agree to participate that they may not receive medication, but they are not told which group they are in until the end of the study. In a good study the researchers are also not told who is getting the medication and who is not). The studies that the committee found on ASD and GI disorders were either poorly controlled (maybe patients were told which group they were in, or maybe the researchers knew. Either way this could influence the results) or uncontrolled (maybe all the participants were on the medication and there was no control un-medicated group. In this case there is no way to see if the effect is due to the medication alone).
Apologies if you knew these things already, I just want to lay out a detailed description of that first statement so everyone can understand the possibilities and limitations of this article. If you have questions or comments so far, please leave a note in the comments section or contact me at firstname.lastname@example.org. Breakfast is calling, so later today, pt. 2 and the consensus statements.