The authors of this paper point to an interesting study by Robin Damrad-Frye and James Laird in the August 1989 issue of the Journal of Personality and Social Psychology. In this study, participants had to listen to a tape of a person reading a Psychology Today article. In the next room, there was a television soundtrack from a soap opera playing. For some groups listening to the article, the TV was very loud and distracting, for others it was barely noticeable, and for some it was not playing at all. After listening to the article, people rated their boredom during the study. 
Second, boredom typically occurs when people have trouble focusing their attention and they believe the reason for this difficulty is in the environment. When sitting in the airport, for example, there is probably a lot going on. There are people having conversations that you could listen to. You probably have something to read. There may be televisions showing the news. But, the stress of waiting for a delayed flight often makes it hard to concentrate, and so your mind jumps from one thing to another. You assume that this is caused by the environment, and so you feel boredom.
In contexts where one is confined, spatially or otherwise, boredom may be met with various religious activities, not because religion would want to associate itself with tedium, but rather, partly because boredom may be taken as the essential human condition, to which God, wisdom, or morality are the ultimate answers. Many existentialist philosophers, like Arthur Schopenhauer, espouse this view. This view of religiosity among boredom does affect how often people are bored. People who had a higher religiosity while performing boring task, reported less boredom than people of less religiosity. People performing the meaningless task had to search less for meaning.[24]

Erich Fromm and other thinkers of critical theory speak of boredom as a common psychological response to industrial society, where people are required to engage in alienated labor. According to Fromm, boredom is "perhaps the most important source of aggression and destructiveness today." For Fromm, the search for thrills and novelty that characterizes consumer culture are not solutions to boredom, but mere distractions from boredom which, he argues, continues unconsciously.[29] Above and beyond taste and character, the universal case of boredom consists in any instance of waiting, as Heidegger noted, such as in line, for someone else to arrive or finish a task, or while one is travelling somewhere. The automobile requires fast reflexes, making its operator busy and hence, perhaps for other reasons as well, making the ride more tedious despite being over sooner.

“Alcohol makes other people less tedious, and food less bland, and can help provide what the Greeks called entheos, or the slight buzz of inspiration when reading or writing. The only worthwhile miracle in the New Testament—the transmutation of water into wine during the wedding at Cana—is a tribute to the persistence of Hellenism in an otherwise austere Judaea. The same applies to the seder at Passover, which is obviously modeled on the Platonic symposium: questions are asked (especially of the young) while wine is circulated. No better form of sodality has ever been devised: at Oxford one was positively expected to take wine during tutorials. The tongue must be untied. It's not a coincidence that Omar Khayyam, rebuking and ridiculing the stone-faced Iranian mullahs of his time, pointed to the value of the grape as a mockery of their joyless and sterile regime. Visiting today's Iran, I was delighted to find that citizens made a point of defying the clerical ban on booze, keeping it in their homes for visitors even if they didn't particularly take to it themselves, and bootlegging it with great brio and ingenuity. These small revolutions affirm the human.”
Boredom is similar to mental fatigue and is caused by repetition and lack of interest in the details of our tasks (such as tasks that require continuous attention, waiting at the airport, prisoners locked in cells). Any experience that is predictable and repetitive becomes boring. In general, too much of the same thing and too little stimulation can cause in its victim an absence of desire and a feeling of entrapment (Toohey, 2012).    

Finally, a real problem caused by boredom is that it leads you to dislike the things that are the object of boredom. In my senior year of high school, for example, I was forced to read Moby Dick. I struggled to get interested in it and spent long hours staring at the pages trying to lose myself in it. To this day, I really do not like Moby Dick. The negative feelings that came with the boredom have stuck to the book.
Lethargy is a state of tiredness, weariness, fatigue, or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to boredom, inadequate sleep, overexertion, overworking, stress, lack of exercise, or a symptom of a disorder. When part of a normal response, lethargy often resolves with rest, adequate sleep, decreased stress, and good nutrition.[21][22]
The French loanword ennui comes from the very same Late Latin word that gave us annoy — inodiare ("to make loathsome"). We borrowed ennui several centuries after absorbing annoy into the language. Ennui deals more with boredom than irritation - and a somewhat specific sort of boredom at that. It generally refers to the feeling of jadedness that can result from living a life of too much ease. The poet Charles Lloyd described it well in his 1823 Stanzas to Ennui when he referred to that world-weary sensation as a "soul-destroying fiend" which visits with its "pale unrest / The chambers of the human breast / Where too much happiness hath fixed its home."