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The most helpful treatment is a combination of psychotherapy and medication. Selective serotonin reuptake inhibitors (SSRIs) are commonly prescribed first. They include fluoxetine, sertraline, paroxetine, citalopram and escitalopram. Other effective antidepressants include bupropion, venlafaxine, mirtazapine and duloxetine.

A number of psychotherapy techniques have been demonstrated to be effective. A technique called cognitive behavioral therapy is designed to help a depressed person recognize negative thinking and teaches techniques for controlling symptoms. Psychodynamic, insight-oriented or interpersonal psychotherapy can help depressed people to sort out conflicts in important relationships or explore the history behind symptoms. 

Options for severe or persistent depression despite the usual medications include electroconvulsive therapy (ECT), ketamine and transcranial medical stimulation. 

There are many variations of both anxiety and depression. Anxiety can be a temporary excessive worry or unease or it can be a more persistent or recurrent psychiatric disorder. The term depression is often loosely used to describe when someone is just feeling down or sad about a situation. The psychiatric definition of depression depends upon specific symptoms. For example, the symptoms of major depression are defined as lasting at least two weeks but usually they go on much longer. Those symptoms include: 
•    Distinctly depressed or irritable mood 
•    Loss of interest or pleasure 
•    Feeling worthless or guilty 
•    Poor concentration or indecisiveness 
•    Thoughts of death, suicide attempts or plans 

Research suggests that depression is not simply a chemical imbalance. It doesn't spring from simply having too much or too little of certain brain chemicals. Rather, there are many possible causes of depression, including faulty mood regulation by the brain, genetic vulnerability, and stressful life events. It's believed that several of these forces interact to bring on depression.

To be sure, chemicals are involved in this process, but it is not a simple matter of one chemical being too low and another too high. Rather, many chemicals are involved, working both inside and outside nerve cells. There are millions, even billions, of chemical reactions that make up the dynamic system that is responsible for your mood, perceptions, and how you experience life.

Hypoxemia is the medical term for a low blood oxygen level. There are many causes but by far most of them are caused by a lung or heart problem. The primary symptom is shortness of breath, but people with hypoxemia will also have less exercise tolerance, feel weak and tire easily. They often have a rapid breathing rate and accelerated heart rate.

Smell disorders are often classified as one of the following:
•    anosmia: complete loss of the ability to detect odors
•    hyposmia: decreased sense of smell with some ability to detect odors
•    dysosmia: distorted sense of smell.
Hyposmia commonly happens as we age. Other causes of loss of smell or distorted smell include:
•    COVID-19 or a cold or sinus infection
•    hay fever (allergic rhinitis)
•    nasal polyps
•    a medication, such as the cholesterol-lowering drug atorvastatin (Lipitor), the blood pressure drug amlodipine or the antibiotic erythromycin
•    a side effect of general anesthesia.

The best remedy for headaches is the one that works best for you. It could be just lying down in dark, quiet room. For people with migraine, taking preventive medicine daily can be very effective. If you do use medication, take it as soon as your feel the headache about to come on. An inexpensive over-the-counter product that contains aspirin, acetaminophen and caffeine works well for many people.