How to use 'besides' correctly
Students often use 'besides' at the beginning of a sentence in place of more formal expressions such as 'in addition to' or 'moreover'. Take a look at this extract from an essay about the association between video games and youth violence:
Research shows that in the same period sales of video games rose by 204%, but the number of murders committed by children dropped by 24% (Lofgren, 2015), suggesting that playing video games may make children less violent. Besides, as Ferguson (2011) mentions, during the time video games were becoming popular, conflicts in schools decreased by 18%, and children committed only half the number of crimes at the end of the period compared to the beginning.
'Besides' is rather informal and has the sense of 'and another thing', as in the examples below:
I am so over that loser Mark. I am glad we broke up. Besides, I have got a new boyfriend - his name is Marcus and he's so sophisticated! He's never even been to McDonalds.
The doctor said I should give up smoking. I think it's a good idea. Besides, I think I might be pregnant.*
In academic writing, it is much better to use more formal expressions. Stick to 'in addition', 'moreover' or 'furthermore' if you want to make an extra point.
*See this video. It's hilarious.