Now 27, Archie wants to be open about his illness now because it is the source of his problem, Mr Lamb said.
As a young music producer Archie discovered pop star Tinchy Stryder, and is now clean, Mr Lamb said.
‘Not unique’
He referred to the issue of mental health when he took to the stage at the Liberal Democrats’ spring conference in Liverpool.
“My family has had our own experience of mental health problems, as our oldest son was diagnosed with obsessive compulsive disorder at the age of 15,” Mr Lamb said.
“It’s something he has made a decision himself to be open about.
“This has been a very painful time for our family. As a parent you just want to keep your children safe, to look out for them and to know that they are going to be OK.
“But my family is not unique. Our experience has made me even more determined to bring mental health out of the shadows and to fight for better care for all of the families affected.”