Many of us can empathise with that feeling of keeping stuff for years and years.

We might keep treasured objects with real sentimental value, or we might have items for a long time - and yet we can't really explain why.

For those of us who don’t like getting rid of our belongings, life can feel very full of stuff.

But when does a tendency to hold on to things become more worrying?

It can be difficult to put a figure on just how many people have what's known as hoarding disorder but it was classified as a mental health condition in 2013.

So what causes this complex and little discussed issue – and is it more than just a problem of too much stuff?

Claudia visits a woman who describes how hoarding has taken over her life to the extent that she doesn’t let anyone into her home. We also meet her psychologist to understand what underpins hoarding disorder and how it’s treated.

And joining us in the studio is Daryl O’Connor, professor of psychology at the University of Leeds, who brings an intriguing study about a phenomenon known as “environmental sensitivity”.

He explains what it is and its new-found links with very common mental health conditions.

Presenter: Claudia Hammond

Details of organisations offering help and support with mental health or self-harm are available at bbc.co.uk/actionline.