What are the negative affects of substance use and abuse?

ansewer please

I'm assuming by use, you mean too much? And by substance, any drug or alcohol? K.
First and foremost, when abusing any substance it becomes an obsession, the most important thing. Do I have enough? Where can I get more? It makes one very, very selfish as having and using is more important than any person, responsibility or job.
Addiction is disease and it is fatal if not treated. Why? Substance use alters our brain. We can physically hurt ourselves by overdosing, accidentally or purposely. They cause health issues, from liver failure, to brain damage to the harm that happens while actually high. Say a person leaves the oven of because they forget about it. They stumble and fall. Huge problems when judgement is gone and someone drives!
Basically the substance will become the single purpose and everything else takes a back seat. It ruins relationships, families, jobs, health and self esteem. That is, if left untreated.

i guess it depends what drug and how long and such, but here it goes
(this could happen, theres not 'if you do this...this will happen)
-causes mental disorders
-causes either increase in apetite or decrease
-causes you to scratch away at your skin
-warped perseption of the world
-brusises
-collapsed vains
-loss of smell
-emphzemia
-liver problems
-kills brain cells