Previously blamed for cognitive deficits in children, so called third hand smoke, the nicotine residue from tobacco smoke that clings to virtually all surfaces long after a cigarette has been extinguished, also reacts with the common indoor air pollutant nitrous acid to produce cancer causing carcinogenic tobacco-specific nitrosamines (TSNAs), according to a new study appearing in PNAS.

A new study published in Current Alzheimer Research claims that marijuana doesn't temper or reverse the effects of Alzheimer's disease and may even cause harm. The findings could lower expectations about the benefits of medical marijuana in combating various cognitive diseases and help redirect future research to more promising therapeutics.

Previous studies using animal models showed that HU210, a synthetic form of the compounds found in marijuana, reduced the toxicity of plaques and promoted the growth of new neurons. Those studies used rats carrying amyloid protein, the toxin that forms plaques in the brains of Alzheimer's victims.