¶ … Hijacked Brain You can be both physically dependent (addicted) and psychological dependent on a substance. Or you have only one type of dependence. For instance, you might be psychologically dependent on your teddy bear or a cup of chamomile tea at bedtime, and believe you can't possibly go to sleep without it. How do you know if you are physically dependent upon a substance?

Probably the most obvious symptom of physical addiction is the onset of symptoms of withdrawal, if the addict attempts to stop using the drug. Psychological dependence may produce physical symptoms caused by the anxiety that is created by stopping...

But the symptoms of physical addiction are so unpleasant that even if the individual wishes to stop using drugs, because his or her liberty, job, or family is at risk, it is still extremely difficult to do so, because the effects on the body of withdrawal are so unpleasant.
Which neural pathway (brain circuit) do potentially addictive substances act upon? Which brain chemical (neurotransmitter) is involved?

Addictive substances affect the neural pathways that release dopamine and stimulate the release of dopamine in the brain in the limbic system of the brain. Or they may prevent dopamine from being…