Smoking affects the whole body- brain, heart, stomach, lungs, mouth, throat, skin, bones and reproductive organs. Many people smoke to reduce their stress but in the long run, smoking alters your brain functioning when it is exposed to regular doses of nicotine and other harmful chemicals. It also leads to thinning of the brain's cortex which further results in problems related to memory and thinking.
With time, your concentration power and focus reduce, you start getting mood swings and you face mood related disorders like anxiety and depression.