I found this on the wikipedia page on [spin isomers of hydrogen](https://en.wikipedia.org/wiki/Spin_isomers_of_hydrogen):

> 
> Parahydrogen is in a lower energy state than is orthohydrogen.
> 
> 
> 

It seem almost like it is obvious but I am having trouble reasoning it out. 

Does it have to do with some magnetic dipole coupling?
Is the difference in energy explained by the exchange energy?