I don't see why it matters if it's a disease, a choice, a combination... It's just like sexuality.
Here's something I just read -
http://www.heretical.com/freudian/coca1884.html
Sigmund Freud
From Über Coca, Centralblatt für die ges. Therapie, 2, pp. 289314, 1884
V. The Effect of Coca on the Healthy Human Body
I have carried out experiments and studied, in myself and others, the effect of coca on the healthy human body; my findings agree fundamentally with Mantegazzas description of the effect of coca leaves.
The first time I took 0.05cg. of cocaďnum muriaticum in a 1% water solution was when I was feeling slightly out of sorts from fatigue. This solution is rather viscous, somewhat opalescent, and has a strange aromatic smell. At first it has a bitter taste, which yields afterwards to a series of very pleasant aromatic flavors. Dry cocaine salt has the same smell and taste, but to a more concentrated degree.
A few minutes after taking cocaine, one experiences a sudden exhilaration and feeling of lightness. One feels a certain furriness on the lips and palate, followed by a feeling of warmth in the same areas; if one now drinks cold water, it feels warm on the lips and cold in the throat. On other occasions the predominant feeling is a rather pleasant coolness in the mouth and throat.
During this first trial I experienced a short period of toxic effects, which did not recur in subsequent experiments. Breathing became slower and deeper and I felt tired and sleepy; I yawned frequently and felt somewhat dull. After a few minutes the actual cocaine euphoria began, introduced by repeated cooling eructation. Immediately after taking the cocaine I noticed a slight slackening of the pulse and later a moderate increase.
I have observed the same physical signs of the effect of cocaine in others, mostly people of my own age. The most constant symptom proved to be the repeated cooling eructation. This is often accompanied by a rumbling which must originate from high up in the intestine; two of the people I observed, who said they were able to recognize movements of their stomachs, declared emphatically that they had repeatedly detected such movements. Often, at the outset of the cocaine effect, the subjects alleged that they experienced an intense feeling of heat in the head. I noticed this in myself as well in the course of some later experiments, but on other occasions it was absent. In only two cases did coca give rise to dizziness. On the whole the toxic effects of coca are of short duration, and much less intense than those produced by effective doses of quinine or salicylate of soda; they seem to become even weaker after repeated use of cocaine.
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There are said to be people who cannot tolerate coca at all; on the other hand, I have found not a few who remained unaffected by 5cg, which for me and others is an effective dose.
The psychic effect of cocaďnum muriaticum in doses of 0.050.10g consists of exhilaration and lasting euphoria, which does not differ in any way from the normal euphoria of a healthy person. The feeling of excitement which accompanies stimulus by alcohol is completely lacking; the characteristic urge for immediate activity which alcohol produces is also absent. One senses an increase of self-control and feels more vigorous and more capable of work; on the other hand, if one works, one misses that heightening of the mental powers which alcohol, tea, or coffee induce. One is simply normal, and soon finds it difficult to believe that one is under the influence of any drug at all.
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I have tested this effect of coca, which wards off hunger, sleep, and fatigue and steels one to intellectual effort, some dozen times on myself; I had no opportunity to engage in physical work.
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The effect of a moderate dose of coca fades away so gradually that, in normal circumstances, it is difficult to define its duration. If one works intensively while under the influence of coca, after from three to five hours there is a decline in the feeling of well-being, and a further dose of coca is necessary in order to ward off fatigue. The effect of coca seems to last longer if no heavy muscular work is undertaken. Opinion is unanimous that the euphoria induced by coca is not followed by any feeling of lassitude or other state of depression. I should be inclined to think that after moderate doses (0.050.10g) a part at least of the coca effect lasts for over twenty-four hours. In my own case, at any rate, I have noticed that even on the day after taking coca my condition compares favorably with the norm. I should be inclined to explain the possibility of a lasting gain in strength, such as has often been claimed for coca by the totality of such effects.
It seems probable, in the light of reports which I shall refer to later, that coca, if used protractedly but in moderation, is not detrimental to the body. Von Anrep treated animals for thirty days with moderate doses of cocaine and detected no detrimental effects on their bodily functions. It seems to me noteworthy and I discovered this in myself and in other observers who were capable of judging such things that a first dose or even repeated doses of coca produce no compulsive desire to use the stimulant further; on the contrary, one feels a certain unmotivated aversion to the substance.
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Coca is a far more potent and far less harmful stimulant than alcohol, and its widespread utilization is hindered at present only by its high cost.
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Like Mantegazza and Frankl, I have experienced personally how the painful symptoms attendant upon large meals viz, a feeling of pressure and fullness in the stomach, discomfort and a disinclination to work disappear with eructation following small doses of cocaine (0.0250.05). Time and again I have brought such relief to my colleagues; and twice I observed how the nausea resulting from gastronomic excesses responded in a short time to the effects of cocaine, and gave way to a normal desire to eat and a feeling of bodily well-being. I have also learned to spare myself stomach troubles by adding a small amount of cocaine to salicylate of soda.
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Accordingly, I should say that the use of coca is definitely indicated in cases of atomic digestive weakness and the so-called nervous stomach disorders; in such cases it is possible to achieve not merely a relief of the symptoms but a lasting improvement.
c) Coca in cachexia. Long-term use of coca is further strongly recommended and allegedly has been tried with success in all diseases which involve degeneration of the tissues, such as severe anemia, phthisis, long-lasting febrile diseases, etc.; and also during recovery from such diseases.
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I once had occasion to observe the case of a man who was subjected to the type of cure involving the sudden withdrawal of morphine, assisted by the use of coca; the same patient had suffered severe symptoms as a result of abstinence in the course of a previous cure. This time his condition was tolerable; in particular, there was no sign of depression or nausea as long as the effects of coca lasted; chills and diarrhea were now the only permanent symptoms of his abstinence. The patient was not bedridden, and could function normally. During the first days of the cure he consumed 3dg of cocaďnum muriaticum daily, and after ten days he was able to dispense with the coca treatment altogether.
The treatment of morphine addiction with coca does not, therefore, result merely in the exchange of one kind of addiction for another it does not turn the morphine addict into a coquero; the use of coca is only temporary. Moreover, I do not think that it is the general toughening effect of coca which enables the system weakened by morphine to withstand, at the cost of only insignificant symptoms, the withdrawal of morphine. I am rather inclined to assume that coca has a directly antagonistic effect on morphine...
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f) Coca as an aphrodisiac. The natives of South America, who represented their goddess of love with coca leaves in her hand, did not doubt the stimulative effect of coca on the genitalia. Mantegazza confirms that the coqueros sustain a high degree of potency right into old age; he even reports cases of the restoration of potency and the disappearance of functional weaknesses following the use of coca, although he does not believe that coca would produce such an effect in all individuals. Marvaud emphatically supports the view that coca has a stimulative effect; other writers strongly recommend coca as a remedy for occasional functional weaknesses and temporary exhaustion; and Bentley reports on a case of this type in which coca was responsible for the cure.
Among the persons to whom I have given coca, three reported violent sexual excitement which they unhesitatingly attributed to the coca. A young writer, who was enabled by treatment with coca to resume his work after a longish illness, gave up using the drug because of the undesirable secondary effects which it had on him.
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Most Alcoholics do. 
