Snorting methamphetamine may and often does irritate the nasal passages.
Some crack cocaine users become more sensitive to crack the longer they take the drug.
PCP users often experience several unpleasant psychological effects, with symptoms mimicking schizophrenia (delusions, hallucinations, disordered thinking and extreme anxiety).
Opiate addicted individuals often cannot hold jobs and may even be involved in crime to pay for their addiction.