Digest of terms
chemical substances, found and used throughout human history, ingested or injected to induce a sought-after mental or physical sensation. Commonly known as 'uppers and downers' i.e. with the properties of providing distinctive stimulation and cheer, or calming, pain-killing and sleep. Some religions have been ardent advocates of certain drugs, as believed to at least simulate mystical experience.
Moral sensitivity in regard to their use arises from the extent to which they have a short or long term effect, and on how desirable or harmful that is. Excessive use of anti-depressants or of the 'chemical cosh' in the treatment of mental illness is widely condemned as de-humanising. But an anti-depressant may enable a person to live and work when without it that would be impossible; even more so with the use of chemical 're-balancing' in the case of schizophrenia.
The medical use of opium, or its equivalents, to numb pain has not ceased after the time of Karl Marx when he cited it as a parallel to religion. Then as now Marx might say that morally both are questionable, but unless debilitating of the capacity for any other change, they are desirable in the absence of any better alternative.
In comparison with 'heavy' drugs, sensitivity against use of tea and coffee on the part of Seventh Day Adventists and Mormons is expressly wary of the impact of stimulants on the balance of body chemistry. Their discernible impact may be open to question, but comparable ingestion of chemicals in drinks leading to hyper-activity in children is well documented in the likes of cola, so questions of consistency arise.
One critical consideration is the role of drugs in creating dependency and addiction, and thus to causing identifiable harm (liberty limiting principles). Human propensity to become addicted is not open to doubt. Its potency has a direct link to the question of moral freedom and responsibility.
See Concept Scenarios.