I know, and know of, people who said they have taken a hit of crack and never tried it again. I overheard one woman in LA say she took one hit and it mad her feel so good, she was afraid to try it again. I am not a doctor, but I do believe that if one is predisposed to addiction, taking one hit may be all it takes. Certainly that is how it worked out for me.
I believe I accepted the first hit of crack because I am an addict, and that's what addicts do. There was nothing extraordinary going on in my life at the time - nothing beyond the normal pressures and ups and downs that all people face. I did not believe I would be hooked. I think that is probably true of most addicts and alcoholics. I haven't met anyone yet who said he or she took their first hit or drink knowing or even suspecting they would drink alcoholically or become addicted.
I believe I was born an addict, and alcoholic. The first time I drank alcohol, I just wanted more and more. During my teens and early 20s I did not drink often, but when I did, it was with great gusto. That is, I always drank enough to get drink.
No one can help an alcoholic or addict until he or she is ready to try to get better.