I'd like more specific info on his illness, but it seems to me that ML and/or the band wish to keep it private, and I respect this.
Anxiety sucks. I've had a bout with anxiety myself. It's horrible! You feel tension all over, you can't sleep. It can be quite debilitating. I had it when my job was putting an enormous amount of pressure on me. Basically too much work to do for one person, exhaustion from working so hard/long hours, no one to help, constant increasing demands, and disaster clearly looming in front of you if you didn't accomplish projects you had no time to do. Everyone had stock options riding on the success of the company. In a real way, if you failed, you let down all those people and their families. The weight of that riding on your shoulders. A recipe for anxiety.
I actually developed physical symptoms such as tendonitis and required physical therapy. I still managed to tough my way through and keep the wheels on until, finally, the company hired some more people to help me and take over some of the jobs I was doing.
The whole experience left some mental scars I'm still not completely over today (I sometimes suffer some anxiety when presented with a large project, etc, with a lot of responsibility). It has also taught me to never let anyone put me in a situation like that again.
I wouldn't wish that sort of mental pain on my worst enemy, let alone ML. I wonder what is causing ML's anxiety ? Perhaps his health coupled with the pressure to perform well and not let the band down ?
I hope he conquers all this.