Age of the Father and Marijuana Use in Adolescence

• Is the age of the father important in terms of the genetics of his children? A recent study in Iceland, where detailed family records date back to the early 1700s, is providing an answer to this question. Researchers analyzed the number of gene mutations in 78 pairs of parents and their living offspring, including a number of grandchildren. The egg and sperm that give rise to a child almost always contain a few mutations. In the Icelandic study it was found that the older the father, the more mutations their sperm conveyed to offspring, while the number of mutations in mother’s eggs remained relatively constant at about 14. A 20-year-old father transmitted about 29 mutations, 30-year-old fathers conveyed 49, and 40-year-old fathers transmitted an average of 69 mutations. Previous studies have shown a relationship between older fathers and the incidence of schizophrenia and autism in their offspring. This suggests that younger men might consider having some of their sperm frozen for later use (insemination) when they decide to mate and have children. (Kong, et al, Nature, Aug. 23, 2012; The Economist, Aug. 25, 2012)

• During childhood and adolescence, a great deal of remodeling occurs in the human brain, including the dying off of groups of neurons and the establishment of new and refined neural circuits. As a result, during this period the brain is extra sensitive to environmental conditions which may affect brain function in adulthood. A new study shows that regular use of marijuana before age 18 can result in diminished mental abilities in adulthood (including lowered intelligence, memory, and decreased attention span). Led by Madeline Meir of Duke University, an international team of researchers tested 1,000 individuals who started using marijuana in adolescence and used it for years afterward. Scores on intelligence tests given at ages 13 and 38 showed an average decline of eight points. The authors point out, “While 8 IQ points may not sound like a lot on a scale where 100 is the mean, a loss from an IQ of 100 to 92 represents a drop from being in the 50th percentile to being in the 29th.”

At age 38, pot-smoking individuals also took tests to evaluate memory, processing speed, reasoning, and visual processing. Those who persistently smoked marijuana in their teens scored worse on most of the tests compared to non-users. Interviews with friends and relatives of those individuals indicated that they often tended to lose focus and forget to do tasks. Study subjects who did not begin using marijuana until they were adults showed no loss of brain function. (Meier, M., Proc. of the National Academy of Sciences (On Line), Aug. 27, 2012)

• Levels of ozone existing in the most polluted cities can cause dangerous changes in heart action. Twenty-three healthy young volunteers were placed in chambers for two hours and breathed an ozone level comparable to that occurring in Los Angeles. Their hearts showed signs of inflammation and rhythm changes. In another study, for two hours on two separate days, male and female subjects breathed clean air or air containing ozone at peak levels in Los Angeles, Houston, Beijing, and Mexico City. Blood levels of several inflammatory agents increased after ozone exposure. Such studies conclude that ozone exposure can trigger inflammation and heart changes in healthy volunteers. (Science News, July 28, 2012; Devlin et al, in Circulation, June 25, 2012)