I&#x27;m surprised no one has brought up lead - childhood lead exposure leads to more rash behavior, and the drop in teen pregnancy starts roughly when the first children who were born after the removal of lead from gasoline and paint started would have become teenagers.<p><a href="http:&#x2F;&#x2F;www.motherjones.com&#x2F;kevin-drum&#x2F;2012&#x2F;02&#x2F;unleaded-gasoline-and-teen-pregnancy" rel="nofollow">http:&#x2F;&#x2F;www.motherjones.com&#x2F;kevin-drum&#x2F;2012&#x2F;02&#x2F;unleaded-gasol...</a>