Addiction to learning
We are born in love with learning. That love usually wanes fast during the years of compulsory schooling. The longer we can sustain the love of learning, the bigger the benefit for the brain, health and mankind. Love of learning has nothing to do with addiction. The definition of addiction includes adverse consequences that are a result of compulsive engagement in an activity.
Negative side effects of learning are tiny in comparison to benefits. If there is a degree of voracity or even compulsion, it can boost the positive effects even further. It is possible to boost one's love of learning. Good learning provides the best boost to further learning.
Learning and gambling
There is a close connection between the reward systems involved in learning and in gambling. Gambling and learning new words both activate the ventral striatum in a similar fashion. This close connection with gambling may confuse the picture for learning. A gambler at a slot machine does not learn much. Addictive videogaming is better. It can be pretty educational. Many team game addicts achieve fluency in English having made no progress at school before. Addiction to sports news may also involve a degree of learning. I learned about Cabinda only during the Africa Cup of Nations (football). Addiction to Facebook updates is not different either. It is based on variable reward in anticipation of specific gains, however, it can also involve a great degree of learning. That learning may involve gossip, celebrity news, fake news, or actual useful learning. Even political poll updates can cause an addiction. In the battle between Hillary Clinton and Donald Trump, the polls were balanced enough to produce the cliffhanger effect. Compulsive checks for new polls have all hallmarks of an addiction. This kind of addiction, however, can lead to a great deal of learning. It is up to the student to separate gambling from learning. Voracious learning is good. Learning derived from an addiction may be good too. However, gambling on its own brings little value to human existence.
Learning and sleep
Obsessive learning may encroach on sleep time, and may contribute to the epidemic of insomnia and DSPS. Creative minds with powerful learn drive may stay up learning till the early morning hours. This violation of sleep pattern was difficult or impossible before the arrival of electric lighting. The good news is that the learn drive tends to wane with network fatigue. The longer we learn, the greater the degree of saturation in memory circuits. Only sleep can bring relief. This is why even most voracious learners tend to get sleepy and give up learning at some point. If a reader skips the night over a novel, this may be a likely combination of insufficient sleep drive, reduced learning, and increased variable reward that is typical of suspenseful fiction.
Learning and exercise
I hear that obsessive learning can lead to less exercise. That would be bad. However, I think that it is bad learning that is more likely to have this effect. Good learning is joyous and sparks extra energy. A happy kid should not survive long sitting over a book or over a computer. There must be a way to vent energy. Perhaps we should rather say that reduced exercise is a hallmark of learning addiction, while good learning has neurotrophic effects and should make one burst with extra energy to burn?
Learning has its cost and it takes time. This is why it should be judicious. However, good learning is nearly always a good long-term investment. This is why we should never fear an addiction. Just the opposite, we should cherish and stoke up the learn drive to provide for happy lifelong learning.