Many forms of depression are best treated by achieving of chemical balance. This may take some time, during which support and care can be essential. Where the depression is primarily emotional, friends can do a lot of listening. Friends should not be used as therapists. However, when someone who knows you well suggests that you need more help, you probably do.
Most people work through their losses at their own pace and without outside help.
However, some people need a therapist who is able to bring losses to the surface where they can be faced and dealt with. Otherwise depression can be expect to return. Those who have also faced depression can often be most helpful. Staying in contact is important to the depressed person because it provides a reality base. Good friends do not allow a friend to suffer alone.