Katy Perry struggles with OCD.

The 'Roar' singer has obsessive compulsive disorder and finds herself inexplicably compelled to organise everything in alphabetical lists and eradicate all germs in her house with crazy cleaning rituals.

Referencing infamous OCD sufferer, movie mogul Howard Hughes, she told Z100 radio host Elvis Duran: "I am so OCD. I always want to put things in alphabetical order. I am also a little Howard Hughes about germs."