Caffeine Drug Addiction
As I once took quite a lot of caffeine(600mg-800mg) and nowadays have cut this down to less than 40mg per day, I thought it'd be worthwhile briefly commenting on it. The DSM already lists Caffeine Withdrawal as a condition, which yes it does exist. If you're addicted, you're gonna get hit with harsh headaches and general fatigue for about a week. Possibly longer. I've heard of some people going a month or 2 generally fatigued from this.
However the DSM does not currently list Caffeine Use Disorder. I've linked below a literature review on it, and it's likely the next version of the DSM will include Caffeine Use Disorder as a condition. From here on out I'll call it an addiction. Symptoms of the addiction include heart palpitations, restlessness, insomnia, inability to dream and anxiety.
In fact the period of time I started to feel a bit agoraphobic was also around the time my caffeine intake was a bit ridiculous. I strongly believe Caffeine is singlehandedly responsible for a lot of the self-reported anxiety we see in society, yet due to how normalised it is, and due to how it's used by teenagers(similar to how they often start using porn in their early teens) they don't remember their baseline normal feeling without it. As a result, all these symptoms get swept away under exam stress, though they're usually not that bad at this point as they are still low intake.
As people enter into adulthood, they sacrifice more sleep, to do more work for their employers and consume more caffeine too. And this once more gets swept under the rug. Consider how a drug addict is often irritable without their drug. Now consider how most people are irritable before their first coffee.
It also goes without saying that it affects your sleep. BADLY. The half life of Caffeine is 5 hours, as a result if you're taking energy drinks to work late at night, you're robbing yourself of hours of good quality sleep. This also affects your dreams too. Caffeine addicts have less dreams, which is probably why more people struggle to remember their dreams nowadays.
I'm not saying all this to say you should quit Caffeine(I have only reduced my intake severely). Do what you want with your life. I'm saying this to direct you straight at it and ask you if you think it is a problem in your life. It could be the source of morning irritability. It could be the source of your anxieties. It could be the source of sleepless nights.
Confront caffeine, the same way you'd confront alcohol and nicotine. As it's normalised, it gets a free pass... and because of this, it wreaks havoc.
Minor Notes
Caffeine use disorder severity is also associated with ADHD symptoms... which may also help describe why there are more diagnoses of ADHD. Especially in Children considering Caffeine is added in plenty of fizzy pop and chocolates for them.
Link
=> Literature Review around Caffeine Use Disorder
=> Caffeine Use Disorder in relation to ADHD