At the core of a brain sickness is a "neuro abuse". Years of "innocent" usage cause a cumulative affect reaching a threshold at certain point.

The list goes typically in the following order:

• Alcohol including some cold remedies that have a high alcohol content
  
• Herbal Drugs & Vitamins (OTC). Our body doesn't need any multi-vitamins if the diet is balanced. Vitamins, minerals, trace-minerals in mega doses become medications and may interact with other prescription drugs. You should prepare in advance and have handy a complete list of your medications, OTC, "naturals" and etc. and bring it always to any doctor appointment. 
  
• Sedatives - insomnia is a common symptom of being under stress, worrying too much about job, health, financial problems and become epidemic in the USA. People accumulate many sleepiness hours until the damage to the brain is irreversible. Some think that a "natural' melatonin is a solution. But real danger in establishing dependence by using barbiturates (phenobarbital,pentobarbital, secobarbital), chloral hydrate, glutethimide, equanil, Miltown, Noludar, Placidyl, Valmid, Quaaludes, Benzodiazepines and many others
• Cold Remedies. It's a well established fact that they do not work but contain dangerous ingridients that may raise your blood pressure or make you drowse and less attentive at work and while driving
• Estrogens 
• Steroids have a perennial appeal but mostly abused causing kidney failure
• Stimulants. This is such a broad category starting from caffein pills to "magic drinks" mixed with amino acids, some herbal stimulants like ginseng. However, this type of remedies are not FDA regulated and basically you don't know the real source, quantity and quality of each ingridient. The real attraction America has is a cocaine which is highly addictive and depletes amount of neurons after a prolonged usage throwing a person to a depression and vicious circle starts again.
• coffee, tea, soft drinks, pain relievers (OTC) come under screaming names like against migraine and severe congestion just to discover the the main active ingredients are reinforced by a solid dose of caffein
• Hallucinogens. LSD, mushrooms (psilocybin), mescaline (peyote), DET, DMT, belladonna alkaloids, PCP, angel dust, ketamine (special K)
• Inhalants (rush, poppers), anesthetics, solvents, sprays and fuels
• Nicotine. Tobacco, chewing nicotine gum, skin path, chewing tobacco, snuff cigarrettes, cigars, pipe tobacco
• Marijuana.Hashish, Hash oil
• Opiates. Opium, heroin (smack, speedballs (opiates with cocaine), morphine, codeine, oxycodone (Percodan), Demerol, Lomotil