Anxiety disorders include the following: Generalised anxiety disorder; Panic disorder; Phobias (agoraphobia, social phobia, specific phobias) Obsessive-compulsive disorder (OCD), Post-traumatic stress disorder (PTSD).

Those with anxiety disorders may self-medicate resulting in a substance use disorder. Conversely, those with substance use disorders may develop anxiety symptoms secondary to their substance use.  The most common period for anxiety symptoms to present in those with drug use problems is during withdrawal, particularly alcohol and benzodiazepines.   Anxiety disorders are exacerbated by stimulants (amphetamines, ecstasy, cocaine and caffeine).

Of those with a primary diagnosis of anxiety disorders, 10 - 30 % may have clinically relevant substance use problems. Those with substance use problems have a 10 - 20% probability of having an independent anxiety disorder although anxiety states and symptoms are associated with about 80% of those in withdrawal within the first 5 days (40% by day 7 and 4% by day 14).

Symptoms

Obsessive-compulsive disorder
Persistent idea or impulse that is neither acceptable nor controllable including anxious feelings and attempts to resist the impulse.
Compulsive acts may be one act or complex ritual.

Phobic disorder
Intense fear and avoidance of an object (simple phobia), situation (agoraphobia), of functioning in situations (social phobia).

Post-traumatic stress disorder
Recurrent dreams, flashbacks and intrusive thoughts related to the originating stress event
Memory problems
Dissociative disorders
Repletion of abusive event by being further abused or abusing others
Generalised anxiety  symptoms

Associated symptoms can include depressive behaviour, guilt, crisis, suicidal thoughts or behaviour, demanding behaviour, self-medicating with legal or illegal drugs.

Pathological anxiety may be a feature of other mental health problems, particularly depression and schizophrenia. Some medical conditions such as an over-active thyroid gland can mimic pathological anxiety.

Treatment

Education
If symptoms present during withdrawal, provide symptomatic relief and reassure that they will almost certainly pass after a few days (symptoms from benzodiazepine withdrawal may last for several weeks).

Explain normal symptoms of "fright, flight and fight" and teach monitoring.

Involve family in treatment, particularly if chronic and resistant to therapy.

Reduce cannabis induced panic attacks by explaining that symptoms of dry mouth and palpitations may be induced by some of the adrenaline like actions of the drug and will pass.

Referral
Specialist interventions required for most of these disorders, particularly PTSD (the most common of the anxiety disorders which is often under-treated).

Cognitive-Behavioural therapy
Use of desensitisation techniques to deal with anxiety-producing stimuli
Self-monitoring
Identification and challenging unhelpful automatic thoughts
Relaxation techniques (eg progressive muscle relaxation, controlled breathing and self-hypnosis
Sleep re-training

Drug therapy
While benzodiazepines are often prescribed, they should be avoided where possible in those with concurrent substance use problems because of their addiction potential.  Other drugs such as buspirone are preferred.

Antidepressants are sometimes used in panic disorder and post-traumatic stress disorder and phobias.

Hyperventilation
Slow breathing down to 14 breaths a minute (one every 4 seconds).  Re-breath into a paper bag to restore normal carbon dioxide concentrations and stop abnormal sensations in arms and feelings of being light-headed.