I had a drug induced psychotic episode in march 2013. i have since recovered but can't concentrate. is methylphenidate suitable for me?

Careful, now: If you had a "drug induced psychotic episode" less than a year ago, i would be observing carefully for any other issues. People with an innate tendency to psychosis are more likely to have these responses. You've also listed citalopram and Abilify (aripiprazole) as current medications. I would not be keen on adding stimulants to you at all, but would review your current medications ; effects more carefully.