How did the African slave trade affect West African societies?I would especially like to know the effects the slave trade had on West Africa

The impact of the slave trade on West African societies
was uneven.  The societies that traded the slaves flourished during the era of the
Atlantic slave trade.  By contrast, the societies from which the slaves were taken were
badly hurt.

The coastal societies got slaves from farther
inland and traded them to the white slavers.  By doing so, the coastal societies became
rich and powerful.  As this was going on, however, the societies farther inland were
drasticaly affected.  Those who came raiding for slaves tended to take the young and the
fit.  These were the most profitable people to take.  Because of this, the most
productive and important members of society (the young, fit workers) were taken away. 
This, of course, harmed the inland societies.