Ultra-processed foods are energy-dense and ready-to-eat food items including things like processed breakfast meats, packaged snacks, and ice cream as well as artificially sweetened drinks.
He can’t say it definitely because, even though the observational results are convincing, you’d want to produce biological/neurological evidence to be able to make the claim with certainty.
“What we found is that consuming high amounts of ultra-processed foods could increase your risk of developing depression by up to 50%”
and
“He said that … they cannot say highly processed food causes depression”
Those statements sound contradictory (Or do they mean that it ‘could’ be 50% or 0%? But if so, why say anything at all)
He can’t say it definitely because, even though the observational results are convincing, you’d want to produce biological/neurological evidence to be able to make the claim with certainty.