London's King's College and Duke Study: Pot Smoking Permanently Lowers IQ

This should should come as no surprise to anyone who has been around users for any length of time...

From Stephen Adams at the Telegraph:

"Researchers found persistent users of the drug, who started smoking it at school, had lower IQ scores as adults.

"They were also significantly more likely to have attention and memory problems in later life, than their peers who abstained.
 

"Furthermore, those who started as teenagers and used it heavily, but quit as adults, did not regain their full mental powers, found academics at King’s College London and Duke University in the US."

[...]

"She [Professor Terrie Moffitt, of KCL’s Institute of Psychiatry, who contributed to the study] said: 'Adolescent-onset cannabis users, but not adult-onset cannabis users, showed marked IQ decline from childhood to adulthood.

"'For example, individuals who started using cannabis in adolescence and used it for years thereafter showed an average eight-point IQ decline.

"'Quitting or reducing cannabis use did not appear to fully restore intellectual functioning among adolescent-onset former persistent cannabis users,' she said.

"Although eight points did not sound much, it was not trivial, she warned.

"It meant that an average person dropped far down the intelligence rankings, so that instead of 50 per cent of the population being more intelligent than them, 71 per cent were."

And what's the drug of choice for professors on college campuses?