Mania manifests with signs that don't match those of ADHD. Among the criteria¹ that characterize a manic episode, only one is directly related to ADHD:
>abnormally and persistently elevated, expansive, or irritable mood
>increased self-esteem or grandiosity
>decreased need for sleep
>more talkative than usual or pressure to keep talking
>flight of ideas or subjective experience that thoughts are racing
>distractibility
>increase in goal-directed activity or psychomotor agitation
>excessive involvement in pleasurable activities that have a high potential for painful consequences
ADHD and manic episode, in more concrete terms:
>disorganized, forgets about appointments, loses stuff, puts off chores and homework, can't sit still for too long, suddenly gets up when not supposed to, finishes other people's sentences, doesn't listen when talked to, can't wait for their turn, interrupts busy people, can't pay attention at all in boring classes, mind thinks about anything but the boring task at hand, makes careless mistakes during exams, suddenly finds something interesting to do and works on it all day, finishes the awesome parts of projects then drops them when only the boring stuff remains, highly distracted by noise and background activity
>grandiose delusions concerning own intelligence, potential and abilities, talks about them at length, becomes highly irritated if contested, thoughts race and feels like brain can't process them, thinks he can do anything (like flying) and engages in high risk behavior as result, sleeps 2 hours then goes jogging at 3 AM unable to understand why everybody else is so slow, relentlessly pursues goals and sexual interests to the point of indiscretion, displays exceptionally poor judgement
Mental afflictions rarely have a clear A or B diagnosis. Comorbidity is common, in that you have a bit of A, some B and flavors of C.
One explanation is that it's an underlying physiological issue: subtle imbalances in brain chemistry with an array of manifestations. We try to figure out what the issues are based on how the software fails to run when in fact there's a HW issue.
Look up comorbity of either of those and depression or sleep disorders etc. Sometimes it's a clear cut this or that but simply because it helps doctors diagnose by pattern matching and we can't actually diagnose neurology properly. We don't have a probe we can use to measure chemical and electrical brain properties, and we don't know how to interpret them even when we can (there are things like fMRI but they say little). So instead we develop a taxonomy of afflictions which tries to be (and doctors act as if it is) made up of distinct entries. If you look into the DSM V (or IV?) manual of disorders you'll see that comorbidities are listed and data shows they're quite common. In my experience most doctors try to slap a diagnosis and treat it without thinking about the non-linear interactions between these issues, caused by the underlying hardware.
They are not the same thing, of course. I was just saying they can both have the problem of focusing and finishing tasks in class as you mentioned. And they can also both have bouts of productivity as the article mentions. I think the article could easily be talking about either, or any other host of things that make learning harder.
I know quite a few people with one or the other. The feeling of being overstimulated is one of the ones that ADHD and bipolar disorder often both share. Someone who is manic can feel like their thoughts are racing, like there's so much they should be doing! So it's hard to focus on what the speaker is saying.
Someone with ADHD can feel like there's so much other more interesting stuff all around them constantly, and their thoughts are wandering over to that song they heard earlier. So it's hard to focus on what the speaker is saying.
Different lines of thought, but the result of "not listening" is the same.
>abnormally and persistently elevated, expansive, or irritable mood
>increased self-esteem or grandiosity
>decreased need for sleep
>more talkative than usual or pressure to keep talking
>flight of ideas or subjective experience that thoughts are racing
>distractibility
>increase in goal-directed activity or psychomotor agitation
>excessive involvement in pleasurable activities that have a high potential for painful consequences
ADHD and manic episode, in more concrete terms:
>disorganized, forgets about appointments, loses stuff, puts off chores and homework, can't sit still for too long, suddenly gets up when not supposed to, finishes other people's sentences, doesn't listen when talked to, can't wait for their turn, interrupts busy people, can't pay attention at all in boring classes, mind thinks about anything but the boring task at hand, makes careless mistakes during exams, suddenly finds something interesting to do and works on it all day, finishes the awesome parts of projects then drops them when only the boring stuff remains, highly distracted by noise and background activity
>grandiose delusions concerning own intelligence, potential and abilities, talks about them at length, becomes highly irritated if contested, thoughts race and feels like brain can't process them, thinks he can do anything (like flying) and engages in high risk behavior as result, sleeps 2 hours then goes jogging at 3 AM unable to understand why everybody else is so slow, relentlessly pursues goals and sexual interests to the point of indiscretion, displays exceptionally poor judgement
¹ https://www.ncbi.nlm.nih.gov/books/NBK64063/#_A92654_