The symptoms for children diagnosed with ADHD can be also be caused by parenting skills, such as not having consistent discipline or rewards systems in place. With younger people having children and then being unprepared to take care of a child may also contribute to the increase in the symptoms of ADHD causing an increase in the diagnosis.
ADHD increased at the same time as the advent of sonagram use on pregnant women.
Has anyone studied the effects on the developing fetus ? It would seem that the sometimes effects of cavitation, bursting or leaking blood vessels,in a developing brain could be causative. Also cell division is affected by frequencies.
Related to "ADHD symptoms may be more noticeable in the modern world," many workers are expected to multi-task today in ways never considered just 25 years ago. How many managers had secretaries to keep them organized, type letters, answer phones, manage schedules, etc. back then? Unless you are very lucky or are upper-level management, office workers do all these things for themselves and are expected to do all things things accurately and efficiently.
Indeed, I believe a new corollary to the Peter Principle has been uncovered: "In an organization, a person rises to the level above the one where they can successfully multi-task." I believe one reason adult ADHD is increasingly diagnosed is that yesterday's coping strategies are less effective in today's world than they used to be because we are all expected to do/juggle more things better and faster. Since those expectations will continue to grow, both at work and in our personal lives, I believe AD/HD will continue to diagnosed--accurately--at an increasing rate in the population.