Question

Autism and Maternal Antidepressant Use A recent study \(^{41}\) compared 298 children with Autism Spectrum Disorder to 1507 randomly selected control children without the disorder. Of the children with autism, 20 of the mothers had used antidepressant drugs during the year before pregnancy or the first trimester of pregnancy. Of the control children, 50 of the mothers had used the drugs. (a) Is there a significant association between prenatal exposure to antidepressant medicine and the risk of autism? Test whether the results are significant at the \(5 \%\) level. (b) Can we conclude that prenatal exposure to antidepressant medicine increases the risk of autism in the child? Why or why not? (c) The article describing the study contains the sentence "No increase in risk was found for mothers with a history of mental health treatment in the absence of prenatal exposure to selective serotonin reuptake inhibitors [antidepressants]." Why did the researchers conduct this extra analysis?

Short answer

The detailed conclusion will depend on the results after performing the Chi-square test in Step 3 and Step 4. Depending on those results, you will decide whether or not there is a significant association between antidepressant use and autism and interpret what this means in the context of the study. As for the additional analysis the researchers performed, it was likely done to control for the potential confounding effect of the mother's psychiatric condition and provide a more accurate picture of the association between autism risk and antidepressant use.

Step-by-step solution

Formulate Hypotheses

Two hypotheses will need to be formulated. Null hypothesis (\(H_o\)): There is no significant association between prenatal exposure to antidepressant medicine and the risk of autism. Alternative hypothesis (\(H_1\)): There is a significant association between prenatal exposure to antidepressants and the risk of autism.

Collect and Arrange Data

The data are already given in the problem. Arrange them into a two-by-two contingency table which will show the relation between autism and maternal antidepressant use.

Perform Chi-Square Test

Calculate your observed chi-square statistic using the chi-square formula, and determine the degrees of freedom (df), which is given by \((R-1)*(C-1)\) where R and C are the number of rows and columns. Then, find the critical value from chi-square distribution table with (df=1) at the \(5 \%\) level of significance.

Make a Decision

If observed chi-square value is greater than critical value, we reject the null hypothesis, else we will accept the null hypothesis.

Interpret the Results

This will conclude whether there is a significant association between prenatal exposure to antidepressant medicine and the risk of autism. Then, for question (b), infer as to whether prenatal exposure to antidepressant medicine increases the risk of autism in the child based on the results from Step 4.

Discuss the Extra Analysis

For question (c), discuss why the researchers conducted this extra analysis, taking into consideration the broader context of the study. Typically, such an analysis is performed to provide more precise and less confounded estimates of the association between maternal antidepressant use and autism risk by adjusting for the potential confounding effect of maternal psychiatric condition.