Mostly an N diagnosis? I've looked and see no research suggesting that, and my experiences contradict it.One of the common traits of ADHD, mostly an N diagnosis, is impending doom. As an N, I can understand this, because I naturally think about how what I'm doing now will impact the future.
Actually what you describe (always thinking of the future) is in a sense the opposite of the ADHD symptom of impulsivity (note: this is not the same as spontaneity. Most spontaneous people have a healthy capacity to become aware of negative potentials of their impulses in the microseconds needed before acting them out). The impulsivity (also called disinhibition) of ADHD means not being aware of any future implications of an impulse in time to prevent it being acted out. The part of the brain that extremely rapidly alerts humans to any likely negative consequences of our immediate impulses is smaller and defective in people with ADHD, so it's more frequently too late to stop us.
The anxiety disorders and sense of impending doom commonly found with untreated ADHD are more likely conditioned by experience. When you live a lifetime of everything you touch turning to shit before you even notice you've touched it, being wound up like a spring in preparation for the worst (we do on average have higher levels of cortisol, the stress hormone, in our blood) is an unfortunate way of compensating for the inability to foresee and prevent painful experiences occurring in the first place.