You were born with a unique view of the world which limits your ability to regulate where your focus lies, but on occasion you can utilize one of its few positives. There are two states that your ADHD stays within. 

Unregulated State (Passive buffs and debuffs): In this state you enjoy some of the benefits to the way your mind works, but unfortunately there are also negatives to this trait.

• Effect 1: You gain advantage on Perception checks, but gain a constant -3 on passive perception.
• Effect 2: You gain a +1 on Wisdom checks, but gain a -1 to Intelligence checks.  

Hyper Focus (Active Ability): In this state you are fully able to focus on what is In front of you with every bit of your focus, but this also takes your focus away from everywhere else. This feature changes it effects based on which situation you are in. This state is also taxing so it can only be done a few times a day. You can utilities this feature a number of times equal to half your proficiency modifier (rounded down) per long rest.

• Situation 1 (in combat):  While in combat you can focus all of your attention onto a single target taking a bonus action, giving you advantage on all attack rolls against the target as well as disadvantage on all attack rolls the target makes against you. But all other enemies also gain this effects against you. This effect last for 1 min.
• Situation 2 (Ability check/saving throw): you can utilize this feature when you are making an ability check or saving throw to give yourself advantage while using your reaction, but when this feature is used this way you gain disadvantage on your next ability check, initiative roll, or saving throw.