Does depression and add/adhd have a lot of similarities?

Not alot, but some: All mental heath problems are likely to have some symptoms in common but it's probably a mistake to make too much (or too little) of that. Difficulty thinking/learning at your best level would be true but for slightly different reasons. Irritability and becoming drained too. Not enjoying some activities and social interactions also. But the medications used are not the same. Why?

Not really: although patients with ADD/ADHD can become depressed until diagnosis is made an treateted. Now BIPOLAR depression is a bit different since the "manic" swings in this disorder can mimic ADD Hope this helps! Dr Z

Yes: They both have underlying imbalance of brain chemicals, . It may include norepinephrine, dopamine, serotonin. Sometimes, they are related to genetic causes in folate (folic acid) metabolism called MTHFR ( the gene for converting folate (folic acid) to its active form that is used to make the brain chemicals).

Yes: Both depression may present with distracibility, difficulty focusing attention and concentrating on tasks. Depression may be mistaken for ADHD. One if the chemical features of ADHD is a low level of not epinephrine in the brain. This is also common in depression.

Yes. Both can cause: a decrease in focus and concentration, irritability and poor organization. Both can lead to procrastination and lowered academic and work performance. There are differences, but you need some guidance to figure this out; meaning, you need a thorough diagnostic procedure to differentiate the two. Check out: http://www.psychologyproductsandservices.com/adhd.html

Yes: They most certainly can. Loss of concentration is specially criteria of both. I encourage you to look at the 9 criteria of depression (basically Google phq9 and the 9 of ADHD hyperactive/impulsive and 9 symptoms of ADHD innattentive type from the DSM 5. (Try a Google search)