Generally, it is a fact that hot drinks make us calm. That is the suggestion from doctors - to drink a hot drink before going to bed. So, is iced coffee stronger because that triggers our metabolism?
From the sources so far (searching on cold VS hot coffee) I have found this:
Grab a cold-brewed coffee before going to the gym. Yes – coffee made from cold water. Surprisingly, cold brew coffee contains many antioxidants and healthy body boosters for better workouts. Skip the shakes and vitamin waters – simply power-up with a cold brew and head for the gym.
The link is given here: http://www.madescolabs.com/accelerate-your-weight-loss-goals-with-cold-brew-coffee/
I am guessing the cold coffee is stronger because of the temperature (metabolism trigger) and not because of a chemical reaction with the substances.
PS: Some examples of cold (iced) coffee can be:
a) The greek frappe which is instant coffee (nescafe mainly), shaken with water and with extra ice cubes added.
b) Freddo Espresso (cold Espresso) which is a double Espresso coffee. It is then blended for 8-10 seconds with 3 big ice cubes. That releases some flavours and the final result is poured into a glass with 1-2 ice cubes.