I’ve been on methylphenidate (concerta) for adult ADHD for 7 months. The first 4 months worked incredibly well but the effects are wearing off already despite increase to 108mg a day! Do all ADHD medications just stop working well after a while. I’m thinking of switching to Vyvanse as that’s the only 2 meds available in the UK. I only sleep every other night and my concentration and super patience is waning, will this just happen after 6 months on Vyvanse or does is vary from person to person?