Dense is a synonym of Thick. Thick is a synonym of Midst. 
Contribution is related to Contribute. Contribute is a type of Promote. Promote is a synonym of Push. Depression is a type of Push. 
Dense <--Synonym--> Thick <--Synonym--> Midst 
Contribution <--RelatedTo--> Contribute --IsA--> Promote <--Synonym--> Push <--IsA-- Depression 