People have two kinds of long-term memory: declarative and procedural. Procedural memory is memory of how to do things, such as how to tie your shoes or ride a bike. Declarative memory consists of semantic memory, or memory of facts, and episodic memory, which is memory of events. Medications that affect long-term memory tend to affect declarative memory, while leaving procedural memory intact.
Anticholinergics
Anticholinergics, a class of medications that block the nervous system neurotransmitter acetylcholine, cause long-term memory loss, reports a research team in the July 13, 2010, issue of "Neurology." Some anticholinergics are sold over the counter. These include Benadryl, Dramamine, Excedrin PM, Nytol, Sominex, Tylenol PM and Unisom. Others require a prescription.
The research team followed a population of 1,652 Indianapolis-area African-Americans over the age of 70 for five years. All of the participants had normal cognitive function at the onset of the study. During the five years, the researchers tracked all medications taken by the participants. They found a significant correlation between anticholinergics and long-term mild cognitive impairment, which involves gradual memory loss. Unlike the kind of memory loss that occurs in elderly with dementia, the memory loss that results from anticholinergics may be reversible, says Dr. Malaz Boustani.
Benzodiazepines
In a letter in the July 1989 issue of "Archives of General Psychiatry," Isaac Marks and his team called attention to studies that show that long-term use of benzodiazepines, such as Xanax and Valium, can lead to an enlargement of the cerebral ventricular system, a system in continuation of the inner canal in the spinal cord.
As the study participants were given the drugs as a treatment for anxiety or panic disorder, it is possible that the disorder itself triggered the enlargement. However, later studies were done that showed that the size of the enlargement depended on the dosage taken, suggesting that this group of drugs can cause brain damage. Enlargement of the cerebral ventricular system has also been found in chronic alcoholics, reports Chicago neurologist Jacob Fox.
The kinship in neurological effects of long-term use of tranquilizers and alcohol probably is not a coincidence. Both alcohol and benzodiazepines increase the effect of the body's naturally occurring neurotransmitter gamma amino butyric acid, or GABA. GABA is the body's neurological excitement inhibitor. It serves to counteract excessive neural excitability that could otherwise cause seizures. Alcohol and benzodiazepines bind to neurons that express GABA, causing a strong inhibitory effect. This slows down the neurological system.
The New Exam Drugs
In the 1950s, college students and teachers, truck drivers and runners often took legally manufactured methamphetamine, a stronger form of amphetamine also sold as a "travel drug," to stay alert while studying, driving or performing physically exhausting exercises.
While amphetamine still makes its rounds as a street drug, narcolepsy drugs have become the new amphetamines. College students and teachers use narcolepsy drugs such as modafinil and methylphenidate to improve memory and concentration. Though the exact mechanism is still poorly understood, researchers believe that these psychostimulants enhance dopamine activity in the nervous system by blocking dopamine transporters.
Like cocaine and methylphenidat, which also block dopamine transporters, narcolepsy drugs continued over a long time period can gradually cause "unfelt" long-term sleep deprivation, which ironically can cause cognitive impairment and memory loss due to a slowdown of the generation of new neurons, reports Stanford neurologist Clete Cushida.
References
- Science Daily: Medications Found to Cause Long Term Cognitive Impairment of Aging Brain, Study Finds
- "Toxic Psychiatry"; Peter Breggins; 1991
- "JAMA"; Cerebral Ventricular Enlargement; Jacob Fox et al; July 1976
- Science Daily: Getting on "the GABA Receptor Shuttle" to Treat Anxiety Disorders
- "Sleep Deprivation"; Clete Kushida; 2005
