Gall anogaeth i ddefnyddio sylweddau peryglus gael ei achosi gan amrywiol ffactorau, gan gynnwys geneteg, bioleg, seicoleg a'r amgylchedd.
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10 Ffeithiau Diddorol About The science behind addiction and substance abuse

10 Ffeithiau Diddorol About The science behind addiction and substance abuse