These are fair points to bring up and discuss, however: 1. Correlation vs. causation is unclear. Is the decline in IQ due to the smoking, or did smoking coinci

These are fair points to bring up and discuss, however: 1. Correlation vs. causation is unclear. Is the decline in IQ due to the smoking, or did smoking coincide or even result from other life factors that impact neurological development? Drug use is common among those with certain psychological illnesses, but it may be a coping mechanism as opposed to the cause, or otherwise differently related than what you are suggesting. 2. IQ testing is not a robust measure of intelligence or capability. There are plenty of fantastic criticisms explaining the problems with IQ testing being used in academia. At best, IQ scores are simply a measure of how well subjects perform with the spatial reasoning logical processing methods used in IQ tests, and not wholly representative of the intelligence or capability of the subject.