There was a great review in Neuropsychopharmacology:
Dowling, G. J., Weiss, S. R., & Condon, T. P. (2008). Drugs of abuse and the aging brain. Neuropsychopharmacology, 33(2), 209-218. doi: 10.1038/sj.npp.1301412
No problem. It sounds like your talk is focused on illicit substances, but it also might be helpful to point out that smoking (tobacco) remains a major issue for geriatrics as well.
See: Ossip-Klein, D. J., Pearson, T. A., McIntosh, S., & Orleans, C. T. (1999). Smoking is a geriatric health issue. Nicotine Tob Res, 1(4), 299-300.
You are right, I will explore those angles too. The only thing I remember my grandma with in those days (some 50 something odd years ago) was smoking pipe!
Don't forget alcohol can be an issue as well - physiological changes and concurrent medication may well mean that 'safe' dosages of alcohol are problematic for older persons, also alcohol harms may be cumulative and thus we would expect an over representation among older people.
I did some research on some aspects of this topic about a year and a half ago. I found a good source regarding illicit drug use in aging population. This is the article I found: Changing profile of abused substances by older persons entering treatment in The Journal of Nervous and Mental Disease,2008, 196(12), 896-905. The authors were Lofwall, M.R., Schuster, A., & Strain, E.C.
Most senior citizens are dependent on medical drugs off their doctor, not illicit drugs off drug dealers. Many of these medical drugs would be illegal without a prescription (i.e. are officially scheduled)
Aloha Mr. Adejumo, great topic to shed more light on. I think in regards to elders there should be a clear distinction between drug abuse and drug mis-use that occurs. Then detection tools can be created and used by an elders doctor. Sometimes education on the subject can be addressed in a respectful conversation by a doctor. Good luck
The American Association for Retired Persons may have information on that. They had published in AARP magazine and article on the medical use of marijuana among people ages 40 - up.
I hope you found the information you were looking for. If this is a topic you will be pursuing, you'll definitely want to look into alcohol and prescription medication abuse. This is one of the most rapidly growing problems being discussed right now. Not that the abuse hasn't been here before, but it is now being recognized and considered as its own issue among older populations, rather than those behaviors being accredited to dementia or depression.
NIDA (National Institute on Drug Abuse) has some good information on drug abuse among again populations. Check out their website at www.drugabuse.gov/ (search terms: "older adults drug abuse" will get you relevant results)
Also, check the NCBI - National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/books/NBK64419/) the Treatment Improvement Protocol (TIP) they published that would probably be of good use, and you can download the pdf file free.
For some quick information, check out the article at AddictionInfo: http://www.addictioninfo.org/articles/1080/1/Substance-Abuse-Among-Older-Adults/Page1.html