Just read this and was coming to post it. For those without a subscription, ARTICLE IS FREE, GO READ IT
Basically, Lehner has been manic-depressive and drinking to fight it off for at least his whole career. When he was going through a concussion the drinking was the only thing that would help. He said he often had thoughts of suicide, calling them "real and close".
He spent 9 weeks in a rehab facility this summer, originally for the alcoholism, but then was diagnosed with bipolar disorder, ADHD, and PTSD.
He says that Botteril was incredibly supportive of him while he was going through it, even after the team decided to move on, and still calls him to check in. He also says he was glad to move on, that they needed a new start.
This really colors a lot of what we've seen from him. He sounds really positive at the end. Hopefully this helps him.