Category: F10 F11 F12 F13 F14 F15 F16 F17 F18 F19
F19 — Mental and behavioural disorders due to multiple drug use and use of other psychoactive substances: facilitator sheet
Teaching objective
The classification question F19 answers is not "has this person used several different substances at some point?" (which describes many people) but "is the actual pattern of use so genuinely mixed, indiscriminate, or unidentifiable that assigning it to one specific F1x category would misrepresent the case, rather than simply being more convenient?" If one substance clearly predominates even alongside occasional other use, the specific category for that predominant substance is still the more accurate and more useful classification.
Choose material
Worked example · Case: Whatever was around that night · Case: Mostly alcohol, but he mentioned a few other things too
Worked example
Show scenario
A 30-year-old reports drinking heavily most days for the past year, meeting several dependence-syndrome criteria for alcohol, and separately mentions using cannabis "now and then" at parties a few times a year, with no reported difficulty controlling that occasional use and no cannabis-related harm.
Reveal step 1
Step 1 — Identify what predominates: heavy, near-daily alcohol use meeting several dependence criteria is clearly the dominant pattern.
Reveal step 2
Step 2 — Characterise the additional substance: occasional cannabis use a few times a year, with no control difficulty or harm reported, is incidental rather than a co-equal pattern.
Reveal step 3
Step 3 — Check whether the overall pattern is genuinely chaotic or indiscriminate: it is not — one substance (alcohol) clearly predominates, with a separate, much lighter pattern of occasional cannabis use alongside it.
Reveal step 4
Step 4 — Weigh against F19: applying F19 here would obscure the fact that alcohol dependence syndrome is the clinically significant, classifiable pattern.
Reveal step 5
Conclusion — This is best classified under F10 (dependence syndrome, given alcohol clearly predominates), not F19, because one substance's own specific category remains the more accurate and more clinically useful classification when it clearly predominates.
Comparison points
F19 is distinguished from every specific F1x category by whether the actual pattern of use is genuinely mixed/indiscriminate or the substance genuinely cannot be identified — not merely by a history that happens to include more than one substance.
Misconception prompt
Applying F19 whenever more than one substance is mentioned: "More than one substance is involved, so it must be F19."
Ask the class why this reasoning fails before revealing the explanation below.
Reveal why it fails
F19 is reserved for a genuinely chaotic or indiscriminate pattern of multiple-substance use with no single substance predominating, or for a substance whose specific identity cannot be determined. A history that happens to include more than one substance — where one substance clearly predominates and any other use is occasional or incidental — is still best classified under that predominant substance's own specific category. Defaulting to F19 whenever more than one substance appears anywhere obscures the clinically significant pattern.
Discussion prompts
Prompt 1
Without looking back at the page, state the question that decides whether F19 or a specific substance category applies.
Prompt 2
Name one situation, other than a chaotic mixed pattern, where F19 would be the honest answer.
Prompt 3
Explain in one sentence why mentioning more than one substance in a case does not automatically mean F19 applies.
Summary
F19 applies only when use is genuinely chaotic/indiscriminate across multiple substances with none predominating, or the substance cannot be identified — not whenever more than one substance is mentioned.