Brian Wilson is ''struggling with stuff in [his] head''.

The Beach Boys legend was due to head out on tour for this month's Pet Sounds and Greatest Hits Live tours, but has now posted a lengthy and emotional letter to his website to confirm the shows have been axed, as he needs to take the time to work on his mental health.

In his letter, he wrote: ''I had every intention to do these shows and was excited to get back to performing. I've been in the studio recording and rehearsing with my band and have been feeling better. But then it crept back and I've been struggling with stuff in my head and saying things I don't mean and I don't know why. Its something I've never dealt with before and we can't quite figure it out just yet.''

Brian has been open with his battle with mental illness for ''many decades'', and says that although he's still able to live a ''wonderful, healthy life'', it's not ''good for [him] to be on the road right now''.

He added: ''It is no secret that I have been living with mental illness for many decades,'' he wrote. ''There were times when it was unbearable but with doctors and medications I have been able to live a wonderful, healthy and productive life with support from my family, friends and fans who have helped me through this journey.''

The 76-year-old musician previously postponed his tour last year to have surgery on his back, and said in his recent update that while he feels physically stronger than ever, he's been left ''mentally insecure''.

Writing on his website, the 'Good Vibrations' hitmaker said: ''As you may know in the last year or so I've had 3 surgeries on my back. The surgeries were successful and i'm physically stronger than i've been in a long time.

''However, after my last surgery i started feeling strange and it's been pretty scary for awhile. I was not feeling like myself. Mentally insecure is how I'd describe it. We're not sure what is causing it but i do know that it's not good for me to be on the road right now so I'm heading back to Los Angeles.''

Brian intends on rescheduling the cancelled dates, though as of the time of writing it is not known when he'll be back out on the road.