In general, symptoms of bipolar disorder first appear during a person’s teens or twenties—or sometimes even earlier. Many people don’t receive treatment until much later, often because symptoms were not recognized. But the first signs usually appear early in life.
There are, of course, exceptions to the usual pattern of mood symptoms appearing early in life. You describe one common type of exception. People who use alcohol or other substances heavily during their teens or early adulthood may not notice mood symptoms until they eventually stop using. The mood symptoms were probably there all along, but they were hidden by the effects of alcohol or drug use.
In the short term, it can be difficult to distinguish mood symptoms from symptoms of alcohol or drug withdrawal. Withdrawal from alcohol or benzodiazepine drugs can cause anxiety, agitation, and sleep problems. Withdrawal from cocaine or amphetamines can cause symptoms of depression. However, these withdrawal symptoms should decrease over several weeks. We wouldn’t blame mood symptoms years after stopping alcohol or drugs on withdrawal.
We sometimes use the term “self-medication” to describe alcohol or drug use by people living with a mood disorder. It’s important to explain what we mean by that. We certainly don’t mean that alcohol other commonly abused drugs are effective treatments for mood disorders. We just mean that alcohol or other drugs can mask mood symptoms in the short run, even if they make things worse in the long run. As many people who have lived with mood disorders can testify, alcohol is probably the oldest treatment for mood symptoms, and also one of the least effective!