How should we respond to depression, avolition, anhedonia, and apathy?

How should we respond to depression, avolition, anhedonia, and apathy? I suggest doing a few things to determine and address the fundamental causes and origins of these feelings and symptoms.
First, I would suggest using an herbal anti-depressant, such as St. Johns wort and Ashwaganda. This will help, but it is not a complete long term solution.
Combine herbal therapy with other therapies, practice doing mindfulness meditations and bring into conscious awareness the things and problems that cause the apathy, anhedonia, depression, avolition. Practice doing Dialectical Behavior Therapy Workbooks, this includes acceptance and mindfulness exercises.
Study existential psychotherapy and philosophy to really examine the issues of your existential crisis.   

Here are some resources to learn more about these solutions:  

• Lecture 10 existential      psychotherapy
• Philosophy: Free Courses      Online | Open Culture
• Existentialism – Free iTunes Audio – Mark       Clarence Phillips, U. of New Orleans
• ASHWAGANDHA Supplement:      Usage, Dosage, Side Effects & Benefits - Examine.com | Examine.com
• Hypericum perforatum -      Scientific Review on Usage, Dosage, Side Effects | Examine.com
• The Dialectical Behavior Therapy Skills Workbook: Practical DBT Exercises for Learning Mindfulness, Interpersonal Effectiveness, Emotion Regulation & ... Tolerance (New Harbinger Self-Help Workbook)