go crazy
go insane
go mad
go doolally

Everybody turned and looked at me as if I'd gone mad.

They all looked at her as if she had gone mad.

Both men looked at him as if he'd gone mad.

But the Americans had their own way, which is to make you go mad over a period of time.

She looked at him now as if he'd gone mad.

In my own mind, I asked myself if she had gone mad.

He looked at her as though she had gone mad.

I'm about to go mad and I need some space.

For some time before his death, people thought he was going mad.

God knows what she must have thought when everyone around her started going mad.