AceShowbiz - Actress Casey Wilson feared the worst for her eldest son before he was diagnosed with celiac disease because he was constantly tired and "depressed".
The "Happy Endings" star reveals Max, now four, was found to suffer from the auto-immune condition in January, two years after displaying symptoms of lethargy.
"At 2 years old he seemed... depressed. Melancholy," she wrote in an essay for The New York Times.
"I would often find him lying on the ground, gazing into the middle distance with such a sense of longing it made my heart physically hurt. He slept 14 hours a day, sometimes 16. Even after all that rest, his teacher would report that while the other kids were playing he would lie on the couch and watch, as though he hadn't slept in days."
Max went on to suffer from extreme mood swings and throw "intense tantrums", which left Wilson feeling less than adequate as a mother as she began blaming herself for his behaviour.
It was only after the youngster fractured his leg and suffered a seizure in the car that Wilson sought out blood tests to get to the bottom of her son's health problems - and he was soon diagnosed with celiac disease, which negatively affects sufferers' ability to digest gluten.
"It was a shock, followed by unimaginable relief. We finally had a diagnosis, and in the grand scheme of things it was a very manageable one," Wilson recalled. "We felt lucky it was not something worse."
Wilson and her husband, screenwriter David Caspe, put Max on a gluten-free diet for six months, and the changes in his mood and behaviour have been significant.
"In six months, almost to the day, his truer self emerged," the actress wrote. "His essence is the very same. But he is now an outwardly thriving, happy 4-year-old who is exploding with creativity and bursting with life."
And Wilson, who is also mum to two-year-old Henry, is relieved she never gave up looking for answers, even though she suffered mentally.
"I'm comforted by the fact that following my instincts got us here," she concluded. "Can my instincts often be wrong? Sure... But in the case of my son, I kept asking why and searching for the answer. I'm proud of that."