diff --git a/app/controllers/maps_controller.rb b/app/controllers/maps_controller.rb
index c60b8831..21946f88 100644
--- a/app/controllers/maps_controller.rb
+++ b/app/controllers/maps_controller.rb
@@ -218,15 +218,7 @@ class MapsController < ApplicationController
 
         @map = Map.find(params[:id]).authorize_to_delete(@current)
 
-        if @map 
-            @mappings = @map.mappings
-
-            @mappings.each do |mapping| 
-                mapping.delete
-            end
-
-            @map.delete
-        end
+        @map.delete if @map
 
         respond_to do |format|
             format.json { 
diff --git a/app/controllers/synapses_controller.rb b/app/controllers/synapses_controller.rb
index 3782d336..47d3321e 100644
--- a/app/controllers/synapses_controller.rb
+++ b/app/controllers/synapses_controller.rb
@@ -50,15 +50,7 @@ class SynapsesController < ApplicationController
   def destroy
     @current = current_user
     @synapse = Synapse.find(params[:id]).authorize_to_delete(@current)
-
-    if @synapse
-      @synapse.mappings.each do |m|
-        m.map.touch(:updated_at)
-        m.delete
-      end
-
-      @synapse.delete
-    end
+    @synapse.delete if @synapse
       
     respond_to do |format|
       format.json { head :no_content }
diff --git a/app/controllers/topics_controller.rb b/app/controllers/topics_controller.rb
index 3cc029f9..d73be190 100644
--- a/app/controllers/topics_controller.rb
+++ b/app/controllers/topics_controller.rb
@@ -200,33 +200,7 @@ class TopicsController < ApplicationController
     def destroy
         @current = current_user
         @topic = Topic.find(params[:id]).authorize_to_delete(@current)
-
-        if @topic 
-            @synapses = @topic.synapses
-            @mappings = @topic.mappings
-
-            @synapses.each do |synapse| 
-                synapse.mappings.each do |m|
-
-                    @map = m.map
-                    @map.touch(:updated_at)
-
-                    m.delete
-                end
-
-                synapse.delete
-            end
-
-            @mappings.each do |mapping| 
-
-                @map = mapping.map
-                @map.touch(:updated_at)
-
-                mapping.delete
-            end
-
-            @topic.delete
-        end
+        @topic.delete if @topic
 
         respond_to do |format|
             format.json { head :no_content }
diff --git a/app/models/map.rb b/app/models/map.rb
index ee949676..6262924e 100644
--- a/app/models/map.rb
+++ b/app/models/map.rb
@@ -2,8 +2,8 @@ class Map < ActiveRecord::Base
 
   belongs_to :user
 
-  has_many :topicmappings, -> { Mapping.topicmapping }, class_name: :Mapping
-  has_many :synapsemappings, -> { Mapping.synapsemapping }, class_name: :Mapping
+  has_many :topicmappings, -> { Mapping.topicmapping }, class_name: :Mapping, dependent: :destroy
+  has_many :synapsemappings, -> { Mapping.synapsemapping }, class_name: :Mapping, dependent: :destroy
   has_many :topics, through: :topicmappings
   has_many :synapses, through: :synapsemappings
 
diff --git a/app/models/synapse.rb b/app/models/synapse.rb
index bf3bdab2..10fba6e9 100644
--- a/app/models/synapse.rb
+++ b/app/models/synapse.rb
@@ -5,7 +5,7 @@ class Synapse < ActiveRecord::Base
   belongs_to :topic1, :class_name => "Topic", :foreign_key => "node1_id"
   belongs_to :topic2, :class_name => "Topic", :foreign_key => "node2_id"
 
-  has_many :mappings
+  has_many :mappings, dependent: :destroy
   has_many :maps, :through => :mappings
 
   def user_name
diff --git a/app/models/topic.rb b/app/models/topic.rb
index 078c633e..d28127fa 100644
--- a/app/models/topic.rb
+++ b/app/models/topic.rb
@@ -3,12 +3,12 @@ class Topic < ActiveRecord::Base
 
   belongs_to :user
 
-  has_many :synapses1, :class_name => 'Synapse', :foreign_key => 'node1_id'
-  has_many :synapses2, :class_name => 'Synapse', :foreign_key => 'node2_id'
+  has_many :synapses1, :class_name => 'Synapse', :foreign_key => 'node1_id', dependent: :destroy
+  has_many :synapses2, :class_name => 'Synapse', :foreign_key => 'node2_id', dependent: :destroy
   has_many :topics1, :through => :synapses2, :source => :topic1
   has_many :topics2, :through => :synapses1, :source => :topic2
 
-  has_many :mappings
+  has_many :mappings, dependent: :destroy
   has_many :maps, :through => :mappings
     
   # This method associates the attribute ":image" with a file attachment