Certain factors can result in a change in memory function. However, if left undiagnosed an untreated they can result in irreversible memory impairment. Addiction to certain substances can result in such changes. Most importantly, alcohol has been known to result in short term memory loss which progresses on to amnesia and then a disorder known as Korsakoff’s syndrome, characterized by confabulation which makes up for the gaps in memory.
Drinking can deprive the body of thiamine, or Vitamin B12, which can cause permanent damage to neurons. The chances of an addict developing this deficiency increases with age, as the rate of absorption of this vitamin and other nutrients goes down. A recent study cited in the database of the National Institutes of Health found that people infected with HIV are often heavy drinkers, and this deals a double blow to their short term episodic memory. (Fama et al) Drugs have neuro-toxic and neuro-adaptive effects that lead to cognitive impairment in which memory loss is prominent. Moreover, areas in the brain such as the anterior cingulated and pre-frontal cortex are concerned with drug related memories that lead to drug craving. (Robbins et al)