Washington Post headline “Most antipsychotic drugs prescribed to teens without mental health diagnosis, study says” (from article). From the article: “60 percent of those ages 1-6, 56.7 percent of those ages 7-12, 62 percent of those ages 13-18, and 67.1 percent of young adults, ages 19-24, taking these drugs had no outpatient or inpatient claim indicating a mental disorder diagnosis”.
The implicit notion here seems to be one of surprise and concern: surely people should have a diagnosis before they are given drugs. Interestingly, many philosophers of psychiatry might disagree. Philosophers of psychiatry often complain that most people do not neatly fit classifications, typically they meet the diagnostic criteria for numerous classifications, they exhibit symptoms below the threshold of criteria some classifications, their behaviour changes over time so they no longer fits previously diagnosis, the cut off points required for diagnosis are arbitrary conventions, etc. In essence, many philosophers reject the current categorical approach (you have either have this diagnosis or you do not) and instead prefer a dimensional model (you lie on a continuum with normality, exhibiting a range of symptoms to varying degrees [this is somewhat of a simplification]).
A consequence of the dimensional approach is that classifications are not so important. On a dimensional approach a doctor needs know what symptoms you exhibit, not which classification you does a half-hearted job of describing your symptoms. Surely then prescribing medication without providing a diagnosis is perfectly acceptable.
I personally prefer a categorical approach and plausibly this issue over drugs shows an advantage of categorical classifications. You need meet a set of fairly stringent criteria to get a diagnosis. On one hand this means some people who have some but not all the symptoms go undiagnosed, on the other it means diagnosis cannot be (should not be) handed out to all who want it. If a diagnosis is generally required to prescribe strong medication then we have an additional safety net above and beyond the judgment of a single doctor prescribing drugs since diagnosis usually requires a specialist. Of course, there are times when someone needs medication immediately and cannot wait for diagnosis, but surely that situation would not cover half of all adolescents?