I had an eight year gap and got the second job I applied for, getting to #2 on interview at the first.
What I did have though, was eight years in which I'd improved my qualifications both generally and in a more closely related area and had voluntary work ranging from Brownie leader, Community Music, Conservation Work and Adult Literacy/Numeracy. I also took a punt on getting a recognised First Aid Qualification.
That meant I'd 'done something' in the happy gaps between being ill.
By the time my next application round came along, I'd also got some decent work history where I'd developed some new skills and a shedload of clickthrough to the questions at the end certificates to add to the list.
I'm now another three jobs along and I'm still taking courses that could help at some undesignated point in the future.
Have you considered seeing whether there is a free/cheap introductory first aid course nearby? Some local authorities offer free Mental Health First Aid training, too. Or just spending a day/afternoon each week volunteering with a conservation trust of some kind?
It doesn't just give you something pleasant to do, going out in fresh air, you can learn new skills, you get used to meeting new people (as that's something that falls by the wayside when you're broke and at home), they might provide training - I learned how to use some pretty heavy duty agricultural equipment with mine, which isn't relevant for my job - but the interviewer was most impressed that the short, fat, old bird had recently got herself a chainsaw certificate and had been trained to use brush and stump cutters.