The effects of an addiction can differ very greatly from person to person based on countless factors. First and foremost, the type of addiction can determine which effects someone will experience.
For example, someone who is addicted to heroin will experience very different effects than someone who is addicted to alcohol.
Another factor that can affect the outcome of addiction is the length of time someone has spent abusing the substance. The longer you abuse a substance, the riskier the addiction typically becomes. This can create different effects.
On a similar note, those who are abusing multiple drugs at once or drugs and alcohol will have a different experience than those who are addicted to one substance.
If the person has co-occurring mental health disorders such as anxiety, depression, post traumatic stress disorder (PTSD), or obsessive compulsive disorder, addiction can worsen these issues or feed off them.
That being said, there are several widespread effects that many people experience with addiction.