HARRY: Anxiety. Ever since you were younger, you've struggled with anxiety. There are very many times where you don't want to leave the comfort and safety of your home. You often have panic attacks when in public places, so being with Harry gets a little difficult at times. He understands how hard it is for you to be in the public eye, so much of your dates are very private, and very well hidden.
NIALL: OCD. Everything has to be very precise with you. The pictures on the wall, to the dvds stacked on the shelves in your living room. You absolutely hate messes more than anything, and you're constantly picking things up. Niall gets frustrated with it at times, and will purposely mess things up around the house to annoy you.
ZAYN: Attention Deficit Hyperactivity Disorder (ADHD). You've had ADHD ever since you were a small child, and have taken pills for it practically your whole life. On the rare occasion you forget to take them, you're extremely hyper. You're practically off the walls. You refuse to do most things, you can't sit, and throw temper tantrums.
LOUIS: Tourette's Syndrome. Your case of tourette's isn't the stereotypical kind like swearing or hitting things uncontrollably. It's more of a tic. You tend to blink a lot more than the average person, and every few minutes or so you'll blink a little more vigorously than other times. It's nothing too extreme or too noticeable.
LIAM: Bipolar. You've struggled with bipolar since your later teens. It sort of just came up out of nowhere. You tend to get very frustrated and mad at the simplest of things, and you'll often freak out on Liam. Moments later you'll snuggle up to his side as if nothing had happened. It took a little while for him to get used to, but eventually he brushed it off as nothing. He just lets you yell.