Overdose Deaths In The U.S. By Drug

Most common drugs found in overdose deaths in 2016

Rank	Referent drug1	Number of deaths2	Percent of deaths3
1	Fentanyl	18,335	28.8%
2	Heroin	15,961	25.1%
3	Cocaine	11,316	17.8%
4	Methamphetamine	6,762	10.6%
5	Alprazolam	6,209	9.8%
6	Oxycodone	6,199	9.7%
7	Morphine	5,014	7.9%
8	Methadone	3,493	5.5%
9	Hydrocodone	3,199	5.0%
10	Diazepam	2,022	3.2%

From CNN.

Of these Fentanyl, Heroin, Oxycodone, Morphine, Methadone and Hydrocodone are all opioid related. Their combined percentages in the CNN chart add up to 82.0% but that can't be correct because the other causes combined add up to 41.4% and there would be some drug overdose deaths that are not from the top ten referent drugs. So is Tramadol (2.0%) which is number 14. A significant number of deaths with opioids (perhaps 10%) are suicides.

Cocaine and Methamphetamine, in contrast are general nervous system stimulants. Their combined percentage in the chart is 28.4%. Meth is the drug least often used with other drugs in an overdose death and is used both both opioids and cocaine with some frequency when another drug is used. Cocaine is often used with opioids and sometimes with Xanax. Cocaine and methamphetamine are very rarely used with an intent to commit suicide.

Alprazolam is better known by the brand name Xanax (a sleeping and anti-anxiety drug). Diazepam is best known as Valium and is used for similar purposes to Xanax. Their combined percentage in the chart is 13.0% As more information in the study reveals, however, these drugs almost never caused deaths on their own. The drugs used with them in overdose deaths are predominantly opioids.

Number 11 is Diphenhydramine 3.2% is an over the counter antihistamine often used as a sleep aid.

Number 12 is Clonazepam 2.6%, which is a sedative in the same class of drugs as Valium.

Number 13 is Gabapentin 2.4%, which is used to treat partial seizures, neuropathic pain, hot flashes, and restless legs syndrome.

Number 15 is Amphetamine 1.9%, which is a central nervous system stimulant in the same class of drugs as methamphetamine, which is often used to treat attention deficit hyperactivity disorder (ADHD), narcolepsy (where a person has an uncontrollable urge to sleep), and Parkinson’s disease. It is less potent than Methamphetamine.

I suspect that many of the non-opioid drugs are often used in combination with opioid drugs in cases where overdoses cause death at rates similar to other drugs in the same class.

So basically, the vast majority of overdose deaths in the United States involve opioids, meth or cocaine (the first two of which have legal prescription variants). Most overdose deaths involve at least one legal prescription drug (whether or not it was legally obtained by the person using it).

The source report from the CDC is here. To CNN's credit, the numbers are  in the original source and not in their original incorrect calculation. The original source lists five more drugs with an 11.2% combined amount. Thus, the percentages for the top 15 drugs in the chart add up to 134.6% So, about a third of cases involve two drugs on the list (a bit less since not all drugs are listed and a bit more because some cases will involve more than two drugs).

Actually, the reason that the totals add to more than 100% explained in the notes to the CDC chart is that:

Deaths may involve other drugs in addition to the referent drug (i.e., the one listed). Deaths involving more than one drug (e.g., a death involving both heroin and cocaine) are counted in both totals. 

In more detail:

Drug overdose deaths in 2016 involving multiple drugs 

Table C shows the percentage of drug overdose deaths with concomitant involvement of other drugs for the top 10 drugs involved in drug overdose deaths in 2016. The percentage of deaths with concomitant involvement of other drugs varied by drug. For example, almost all drug overdose deaths involving alprazolam or diazepam (96%) mentioned involvement of other drugs. In contrast, 50% of the drug overdose deaths involving methamphetamine, and 69% of the drug overdose deaths involving fentanyl mentioned involvement of one or more other specific drugs. 

Table D shows the most frequent concomitant drug mentions for each of the top 10 drugs involved in drug overdose deaths in 2016.  

• Two in five overdose deaths involving cocaine also mentioned fentanyl.  

• Nearly one-third of drug overdose deaths involving fentanyl also mentioned heroin (32%).  

• Alprazolam was mentioned in 26% of the overdose deaths involving hydrocodone, 22% of the deaths involving methadone, and 25% of the deaths involving oxycodone.  

• More than one-third of the overdose deaths involving cocaine also mentioned heroin (34%).  

• More than 20% of the overdose deaths involving methamphetamine also mentioned heroin.

So totals grouping multiple drugs may be overstated because some of those percentages may come from the same incident.

Mystery solved.

The percentage of overdose deaths that do not involve at least one opioid drug is fairly modest. It is also worth noting that marijuana is not in the top fifteen causes of drug overdoses and neither are any other psychedelic or "club" drugs (e.g. MDMA and ketamine).