diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index 3318075e9e..5f2e56c9c3 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -310,6 +310,8 @@ module ActiveRecord
         connect
       end
 
+      # Disconnects from the database if already connected. Otherwise, this
+      # method does nothing.
       def disconnect!
         @connection.close rescue nil
       end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index ba7852192e..53ea80cf15 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -276,7 +276,8 @@ module ActiveRecord
         super
       end
 
-      # Close the connection.
+      # Disconnects from the database if already connected. Otherwise, this
+      # method does nothing.
       def disconnect!
         clear_cache!
         @connection.close rescue nil
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
index 326f22ce82..2ceb62dfc2 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
@@ -90,6 +90,8 @@ module ActiveRecord
         sqlite_version >= '3.1.6'
       end
 
+      # Disconnects from the database if already connected. Otherwise, this
+      # method does nothing.
       def disconnect!
         super
         clear_cache!