" Addiction could also be a manipulative response to an underlying condition, such as depression or a nonspecific inability to cope with the stresses of life. In which the abuser uses drugs as a maladaptive way to cope."

This is a good way of explaining it. There is an inability to cope which some of us have as an "underlying condition". This is the part that should be referred to as a dis-ease. Physical addiction to a substance is an attempt to treat that condition (unsuccessfully). I have heard this phenomenon referred to as "an obsession of the mind and an allergy of the body". I have also heard it called a spiritual disease, which would naturally fall outside the realm of empirical enquiry.

While it is necessary for an addict to take responsibility and to choose new behaviors in order to recover, I think the stigma of having "bad character" or being untrustworthy is unfortunate. If we are to find solutions we must let addicts know we care about them as a human being and that they are not damned to be outcastes for life.