Dependence and addiction

To me they're synonyms., but it is

dependence (US ALSO dependance) dependency ON a substance

addiction TO a substance

I think the two words are often used interchangeably. In medical terms, though, I think "addiction" describes a state where actual physiological changes have occured that make it physically as well as emotionally difficult for the person to give up the addictive substance. Maybe someone with medical training can help us out here?

I don't think they are synonyms.

In my opinion, Dependence has broader meaning and sometimes can be used to replace addiction.

The persons/substances you are depend on are necessary to servive.

But, addiction, is a derogatory word and indicates lack of self control. (excessive dependence)

The substances you are addicted to are generally not necessary to servive

Yes, of course dependence has a broader meaning. Right now I can't drive (because of recent surgery) so I am dependent on my family for transportation - but I'm not addicted to it! I didn't mention the broader meanings in my previous post because the original poster specified that his question referred to drugs and alcohol.

The term in rehab. is "chemical dependency", though it is about addiction all right.

Yep, you're right Khoff. The same broader meaning you gave example of can be used in collocation with alchohol or drugs. For example, I had avery bad day and I have guests who I do not like very much for dinner, I can say that I am dependent on alchohol to bear with my guests, though I am not addicted. (I just gave this example to show Manosmaster a related usage.)

Thanks Julie, that was

Yet, I think there's a difference between "I'm dependent on something in a certain context", and "I suffer from a dependency on the same something". I mean, in the second example, my case is more serious... No?

I think I would embrace the thesis of science-guru and khoff. Their examples convinced me.
Thanks again

Koff is correct:

addiction is a pattern of compulsive drug use which is characterised by a craving for drugs - generally opiods - for effects other than pain relief. Sudden withdrawal of the drug leads to severe physical effects, but this is an effect of the drug, not the addiction. Even non-addicted people may suffer withdrawal effects to a minor degree.

The persons/substances you are depend on are necessary to servive.