"Children born in the winter months already have a few strikes against them. Study after study has shown that they test poorly, don't get as far in school, earn less, are less healthy, and don't live as long as children born at other times of year. Researchers have spent years documenting the effect and trying to understand it."The new study (.pdf link) looks at the problem in a new way. Look at the mothers and not the babies.
It is surprising that no one thought to look at the family background and specifically the mothers of the children in the studies. It turns out that winter babies tend to be born to mothers that are unmarried, teenage and less educated. Thus, given the many studies that show that the outcome for a child is strongly correlated with parental education, socio-economic status, marital status, and parental age, it is not surprising that winter babies have a tougher time of it.
In Linus' case (and my own) his mother is married, not teenage and has a college degree, so the "plight" may not apply (never mind the danger of applying statistics to individual outcomes). I suppose that given the statistics we are discussing that makes him ever so slightly unusual compared to the rest of his January birthday cohort.
The next step in the study will be to determine why mothers of babies born in winter have these characteristics. The study suggests a decrease in fertility related to hot months for usually poor families without air conditioning and increased fertility in the cooler spring results in a disproportionate number of winter babies to women with fewer means. Commentors on the article point out that babies born in January are conceived in Spring which is spring break and prom time for teenagers. Just remember that plausible explanations are not always the correct explanations.