What's the earliest evidence of drug abuse?

The way that the question is framed is laced with quite modern conceptions of "abuse" and "drugs" that would be completely incomprehensible for earlier people.

Yet the word 'drug' was not always so closely linked in the public mind with substance abuse. The definition of the noun drug in volume III (published in 1897) of original edition of the Oxford English Dictionary (OED) is as follows:

'An original, simple medicinal substance, organic or inorganic, whether used by itself in its natural condition or prepared by art, or as an ingredient in a medicine or medicament.'

The OED went on to discuss other aspects of the history and use of the term that need not be considered here. From the point of view of this essay, the key fact to note is that the noun drug is associated with medicinal or related use. There is no reference to recreational use or abuse of a substance in the definition.
_{John Parascondola: "The Drug Habit: The Association of the Word 'Drug' with Abuse in American History", in Roy Porter & Mikulas Teich (Eds): "Drugs and narcotics in history", Cambridge University Press: Cambridge, New York, 1995, p156.}

Yet, if we still want to apply our modern protestant understanding to both words and concepts into earlier texts then we find indeed quite some evidence for temperance. That is probably best embodied in ancient laws. Or in other words, notarised disapproval of authorities, the desire to control the behaviour of the subjects in a state. Controlling other people and not wanting others to experience joy is older than dirt, but labelling anything but strict abstinence as abuse is found in pretty much the earliest texts available.

Ancient Civilizations — Descriptions of the evils wrought by drunkenness and efforts to cure them are as old as literature. On the tombs of Beni-Hassan in Egypt, 3,000 years old, pictures are seen of drunken men carried home by their slaves after a feast, and of women also who are manifestly intoxicated. Wine was offered to the gods in connection with rites of the most bestial character. There was at least one advocate of abstinence, one prohibitionist in Egypt, in 2000 BC, Amen-em-an, a priest, who is on record, in a letter to a pupil, as commending his pledge of total abstinence, taken with an oath, and insisting on its observance:

"I, thy superior, forbid thee to go to the taverns. Thou art degraded like the beasts. God regards not the breakers of pledges."

Chinese literature of the same period furnishes like utterances. In 2285 the emperor banished a man for inventing an intoxicant made from rice. Mencius declares that Yao the Great was an abstainer, and that during his reign virtue pervaded the land, and crime was unknown. A few years later, 21st BC, a drunken ruler led the people to drunkenness, which continued and increased for centuries. The anti-treating remedy was tried 202 BC in a law forbidding drinking in companies of more than three.
_{Wilbur Fisk Crafts, Sara Jane Timanus, Mary and Margaret W. Leitch: "Intoxicating drinks & drugs in all lands and times, a twentieth century survey of temperance, based on a symposium of testimony from one hundred missionaries and travelers", International Reform Bureau: Washington, 1911. (Note date & publisher!)}

But how would you label "abuse" in people that were almost all almost constantly inebriated by some kind of substance? In Europe it was quite common to start the day with beer soup and continue through the day likewise, increasing the dose towards night time.

If we go one step further into anachronistic territory and make that definition of "abuse is deviance from strict abstinence" ("just say no!") our own than the oldest evidence for abuse is perhaps more than 60000 years old. In a cave in Iraq/Shanidar IV was a 30–45 year old male laid to rest with everything "drugs" the region had to offer (the stimulant Ephedra yielding an actual chemistry lab precursor for crystal-meth).
_{Elisa Guerra-Doce: "The Origins of Inebriation: Archaeological Evidence of the Consumption of Fermented Beverages and Drugs in Prehistoric Eurasia", Journal of Archaeological Method and Theory, 2015, Vol 22, 3, pp 751–782, p 754.}

This concept of "drug abuse" needs clarification. Otherwise the most accurate answer to the question is that this is a modern invention. Pre-modern societies generally had no use for real sanctions across the board for mind altering substance use (Andy Reymann: "Drogen in vormodernen Gesellschaften"). A paper looking at "the natural history of drug abuse" starts its journey shortly before WWI.

Whether for its nutritive value, keeping quality, safety over potentially contaminated sources of water, use as a medium for medicines, or for the pleasure of its flavor or effect, beer was a staple in ancient Egypt, even described as its "national drink" (Lutz 1922:76). Beer was consumed in Egypt at festivals, included in tombs and burials, and is associated with important deities. The goddess Hathor has the epithet, dubious by modern sensibilities, of "mistress of drunkenness." (Likewise, the Sumerians associated the goddess Ninkasi with beer and brewing and honored her for it.) An Egyptian invocation listed "bread and beer, beef and fowl, alabaster and linen, and all things good " "Bread and beer," referred to food, sustenance, and well-being in general (Darby et al. 1977: 529ff.; Hayes 1953: passim).
_{Jeremy Geller: "Bread and beer in fourth‐millennium Egypt", in: "Food and Foodways: Explorations in the History and Culture of Human Nourishment", 5:3, 255-267, 1993.}

Taking another angle: As it should be clear excessive consumption of anything cannot be "good for you", it stands to reason to look at the earliest voices for public health implications?

During his reign, Huang Di discoursed on medicine, health, lifestyle, nutrition, and Taoist cosmology with his ministers Qi Bo, Lei Gong, and others. Their first discussion began with Huang Di inquiring, “I’ve heard that in the days of old everyone lived one hundred years without showing the usual signs of aging. In our time, however, people age prematurely, living only fifty years. Is this due to a change in the environment, or is it because people have lost the correct way of life?” Qi Bo replied, “In the past, people practiced the Tao, the Way of Life. They understood the principle of balance, of yin and yang, as represented by the transformation of the energies of the universe. Thus, they formulated practices such as Dao-in, an exercise combining stretching, massaging, and breathing to promote energy flow, and meditation to help maintain and harmonize themselves with the universe. They ate a balanced diet at regular times, arose and retired at regular hours, avoided overstressing their bodies and minds, and refrained from overindulgence of all kinds. They maintained well-being of body and mind; thus, it is not surprising that they lived over one hundred years. “These days, people have changed their way of life. They drink wine as though it were water, indulge excessively in destructive activities, drain their jing—the body’s essence that is stored in the kidneys—and deplete their qi. They do not know the secret of conserving their energy and vitality. Seeking emotional excitement and momentary pleasures, people disregard the natural rhythm and order of the universe. They fail to regulate their lifestyle and diet, and sleep improperly. So it is not surprising that they look old at fifty and die soon after.
_{Maoshing Ni: "The Yellow Emperor’s Classic of medicine: a new translation of the Neijing Suwen with commentary", Shambhala: Boston, 1995.}

The Yellow Emperor Huangdi's traditional reign dates are 2697–2597 or 2698–2598 BC. Looking at the usual timelines: according to the best of those timelines that seems to be a first emphasis on possible negative health consequences.