Just my personal observation here: professionals tend to ignore or downplay "mothers feedback". We are pretty much always seen as "over-reporting". It would be interesting to see a study on the accuracy of "mother intuition" when it comes to recognizing problems. I saw problems before age 2. The medical system didn't support me for another 16 years... but it does now.
Are teens with food allergies more likely to have mental health problems? or are teens with mental health problems more likely to have food allergies? It's a bit hard to make a cause-and-effect statement on that front. But, again from personal experience, kids with developmental and/or mental health issues do tend to have food allergies and sensitivities.