Mood stabilizing medication for Anxiety, Depression, ADHD (Attention Deficit Hyperactivity Disorder), OCD (Obsessive-Compulsive Disorder), Bipolar disorder.

Most of these medications work by affecting neurotransmitters in the brain.

Neurotransmitters are types of hormones in the brain that transmit information from one neuron to another. There are approximately 50 neurotransmitters identified. They are made by amino acids. Neurotransmitters control major body functions including movement, emotional response, and the physical ability to experience pleasure and pain. The most familiar neurotransmitters which are thought to play a role in mood regulation are serotonin, norepinephrine, dopamine, acetylcholine, and gamma-aminobutyric acid (GABA).

Different neurotransmitters are involved in different pathways (neurons connecting different areas of the brain).

Neurotransmitter Effects on Mental Health:

• Modulate mood and thought processes
• Control ability to focus, concentrate, and remember things
• Control the appetite center of the brain
• Regulate sleep

Some common neurotransmitters:

• Acetylchlorine helps with memory and learning.
  
• Dopamine is primarily responsible for sex drive, mood, alertness, and movement.
  
• Norepinephrine and epinephrine (adrenaline) influence alertness, arousal, and mood.
  
• Serotonin is involved in mood, appetite control, emotional balance, and impulse control.
  See Serotonin below
• GABA helps with relaxation and sedation. See GABA below.

Benzodiazepines, such as Valium, Ativan and Xanax appear to work by affecting neurotransmitters such as gamma-aminobutyric acid (GABA), a neurotransmitter that suppresses the activity of nerves. Scientists believe that excessive activity of nerves may be the cause of anxiety and other psychological disorders.
GABA has a calming effect on the brain and helps the brain filter out "background noise". It improves mental focus while calming the nerves and regulating anxiety.
It is the most plentiful neurotransmitter. Over half of all brain synapses use it. It regulates norepinephrine, adrenaline, dopamine, and serotonin and is a significant mood modulator.
Benzodiazepines do carry a risk of addiction or tolerance (meaning that higher and higher doses become necessary to achieve the same effect), so they are not as desirable for long-term use.

Selective serotonin reuptake inhibitors (SSRIs), such as, Celexa, Lexapro, Luvox, Paxil, Prozac, Zoloft, and are newer medicines that both act as SSRIs and also affect other serotonin receptors. SSRIs work by blocking reuptake they increase the amount of serotonin, a neurotransmitter that enhances the function of nerve cells in the brain that regulate emotion.
Serotonin is an inhibitory neurotransmitter involved in the regulation of mood, anxiety, libido, compulsivity, headaches, aggression, body temperature, eating disorders, social anxiety, phobias, sleep, appetite, memory and learning, cardiovascular function, muscle contraction, and endocrine regulation.
Stress reduces our serotonin levels as our body uses up serotonin in an attempt to calm itself.
People with generalized anxiety disorder (GAD) experience excessive worry that can in addition to difficulties in concentration cause physical symptoms. Evidence suggests that GAD involves several neurotransmitter systems in the brain, including norepinephrine and serotonin.
Estrogen levels can affect serotonin levels and this may explain why some women have pre-menstrual and menopausal mood problems.
Exercise and exposure to light may increase or stimulate serotonin levels.

Tricyclic antidepressants (TCAs):such as Elavil (amitriptylin), Silenor, increase levels of norepinephrine and serotonin by inhibiting their reuptake, and also block the actions of another neurotransmitter, acetylcholine.

The first-line treatment for acute depression in bipolar patients is lithium or Lamictal (lamotrigine).
Lithium affects the flow of sodium through nerve and muscle cells in the body. Sodium affects excitation. It is thought to help strengthen nerve cell connections in brain regions that are involved in regulating mood, thinking and behavior.

Others:
Desyrel (Trazodone HCL), Zyban (bupropion) See :
Common Anxiety Disorder Medications: Types & Side Effects | RXlist.com

Six out of 10 people will feel better with the first antidepressant they try; however, the other 4 people will need to try another antidepressant until they find the one that is right for them. In addition, most people will need to take an antidepressant regularly for at least 6 weeks until they feel the full effect. You may also need to keep taking them for longer periods of time, even for the rest of your life.

Links:
Neurotransmitters, Depression and Anxiety - Kellevision
Neurotransmitters - causes, effects, drug, people, used, brain, personality, mood | MindDisorders.com
Commonly Prescribed Psychotropic Medications | National Alliance on Mental Illness (NAMI)
Antidepressants | Johns Hopkins Lupus Center
Beyond the Reward Pathway | Genetics at U. of Utah