Systematic Desensitization

Systematic desensitization is a type of exposure therapy, a treatment that helps people face what they fear instead of avoiding it. It is based on the principle of classical conditioning. Joseph Wolpe developed it during the 1950s to treat phobias and anxiety disorders.

It gradually exposes the person to the feared object or situation in a controlled, relaxed setting. Relaxation techniques are paired with a hierarchy of anxiety-causing stimuli, so the person can face each one without an anxiety response.

The therapy removes the fear response to a phobia. It does this through counter-conditioning. The feared object, the conditioned stimulus, comes to trigger relaxation instead of fear.

The patient is counterconditioned, taught a new association that counters the original learned behavior. The new response is relaxation instead of fear, because the two cannot coexist (reciprocal inhibition).

A desensitization hierarchy is constructed, and the patient works through it, visualizing each anxiety-provoking event while engaging in the relaxation response.

The number of sessions required depends on the severity of the phobia. Usually, 4-6 sessions, up to 12 for a severe phobia.

The therapy is complete once the agreed therapeutic goals are met (not necessarily when the person’s fears have been completely removed).

How Desensitization Works

• In vitro – the client imagines exposure to the phobic stimulus.
• In vivo – the client is actually exposed to the phobic stimulus.
• Group – several clients with the same phobia work through a shared hierarchy, an economical format that adds modelling and social support.
• Self-help – the client works through relaxation and a hierarchy largely alone, guided by manuals or recordings.
• Virtual reality – controllable, realistic simulations (a flight, a height) combine the safety of imagination with much of the vividness of real exposure.

In vivo exposure is generally considered more effective than in vitro. In a study of childhood water phobia, in vivo exposure also worked better than vicarious (observational) exposure (Menzies & Clarke, 1993). Real-life exposure is not always practical, though, so in vitro work is still widely used.

The Three-Step Systematic Desensitization Process

1. Relaxation Training: The client learns deep muscle relaxation, breathing exercises and guided imagery to reach a calm state on command.
2. Anxiety Hierarchy: Client and therapist rank fear-inducing situations from least to most frightening, creating the structure the therapy follows.
3. Graded Exposure: Starting at the bottom, the client confronts each step while staying relaxed, moving up only once anxiety fades.

Relaxation training matters because of reciprocal inhibition: two opposite physical states cannot occur at once. Fear tenses the body; relaxation releases it. Anxiety raises heart rate, tenses muscles and quickens breathing, while deep relaxation is its physiological opposite.

As Wolpe (1969) himself put it: “if a response inhibitory of anxiety can be made to occur … it will weaken the bond between these stimuli and the anxiety.” Pairing relaxation with the feared stimulus, again and again, lets calm replace fear as the learned response.

Wolpe’s method rests on two ideas. First, a phobia is a learned response.

A neutral object paired with a frightening experience becomes a conditioned stimulus, a trigger that now provokes fear, as in the Little Albert case (Eysenck & Rachman, 1965). Because the fear is learned, it can in principle be unlearned.

Second, Wolpe drew on laboratory work with cats. He abolished their experimentally induced fear by feeding them, an anxiety-incompatible response, while the fear cue appeared in graded strength (Wolpe, 1958).

Avoidance explains why phobias persist. In Mowrer’s (1960) two-process theory, escaping the feared object is negatively reinforced because it reduces anxiety. Systematic desensitization is designed to break that cycle.

Systematic Desensitization Examples

Applying the three-step process of systematic desensitization to treating a phobia of spiders:

1. Relaxation Training:

   • The individual is first taught relaxation techniques, such as deep breathing, progressive muscle relaxation (Jacobson’s 1938 method of tensing, then releasing, each muscle group in turn), or guided imagery.
   • They practice these techniques until they can achieve a relaxed state consistently on command.

2. Establishment of Anxiety Hierarchy:

   • Together with the therapist, the individual creates a list of situations involving spiders, ranked from least anxiety-provoking to most.
   • Each step is often scored on a 0–100 Subjective Units of Distress Scale (SUDs), from complete calm to the worst imaginable terror.
   • This might look like:
     1. Thinking about a spider.
     2. Looking at a picture of a spider.
     3. Watching a video of a spider.
     4. Being in the same room as a spider inside a closed container.
     5. Watching someone else handle a spider.
     6. Standing close to a spider inside an open container.
     7. Touching a spider with a gloved hand.
     8. Holding a spider with bare hands.

3. Gradual Exposure:

   • The client reaches a state of deep relaxation and is then asked to imagine (or is confronted by) the least threatening situation in the anxiety hierarchy.
   • For example, in a relaxed state, the individual first thinks about a spider. The focus here is on maintaining relaxation despite the thought.
   • Once they can think about spiders without anxiety, they move to the next level, like looking at a picture of a spider while staying relaxed.
   • The process continues, with the individual gradually exposed to more direct interactions with spiders while maintaining their calm, until they can eventually handle a spider without significant fear.
   • If anxiety rises at any step, the client returns to relaxation and, if necessary, drops back a step.
   • Between sessions, clients usually practise in real-life situations as homework, moving from imagination to reality.

Throughout the process, the goal is for the individual to associate spiders with feelings of relaxation rather than fear, eventually diminishing the phobic response.

Case Studies: Wolpe and Little Peter

Wolpe (1964) successfully used the method to treat an 18-year-old male with a severe handwashing compulsion. The disorder involved a fear of contaminating others with urine.

• Problem: After urinating, the patient felt compelled to spend 45 minutes cleaning his genitalia, two hours washing his hands, and four hours showering.
• Imagined exposure: Relaxed, the patient imagined low-anxiety scenes, such as an unknown man touching a trough of water with one drop of urine. As his anxiety dissipated, Wolpe gradually increased the imagined concentration of urine.
• Real-life exposure: A real bottle of urine was presented at a distance and moved closer in gradual steps.
• Outcome: Wolpe could finally apply drops of diluted urine to the back of the patient’s hand without evoking anxiety. A follow-up four years later revealed complete remission of the compulsive behaviors.

A different approach came from Mary Cover-Jones. She studied several children to find the best way to remove fear responses. Her most famous case, known as Little Peter (Jones, 1924), is considered the earliest example of any kind of behavioural treatment.

She brought a caged rabbit progressively closer to Peter while he ate a favourite food. His pleasure in eating counter-conditioned his fear. This graded, food-paired approach was the direct forerunner of Wolpe’s relaxation-paired hierarchy, which he named systematic desensitization decades later.

Common Uses of Systematic Desensitization

Systematic desensitization works best when a clear hierarchy of feared situations can be built:

• Specific phobias: The core, best-validated use, from animals (spiders, snakes, dogs) to heights, enclosed spaces, flying and injections.
• Focal childhood fears: Learned fears tied to identifiable objects or situations, including noise phobia (McGrath et al., 1990).
• Test, dental and needle anxiety: Exam anxiety, dental phobia and blood–injection–injury fears suit graded exposure, because feared cues can be ranked.
• Obsessive-compulsive washing: Wolpe (1964) treated a contamination-driven compulsion. Modern practice more often uses exposure and response prevention.
• Trauma reminders: Graded exposure descended from this method informs trauma treatment, though prolonged exposure and trauma-focused therapy are the front-line options.
• Performance anxiety: Relaxation plus graded exposure helps manage competitive anxiety, such as fear of a particular opponent, venue or skill.

Exposure-Based Variants: Implosion and Flooding

Implosion and flooding are faster, more intense relatives of systematic desensitization, sharing its roots in classical conditioning. Both drop the gradual hierarchy and confront the feared stimulus directly, rather than working up to it step by step.

Anxiety cannot stay at its peak forever.

Implosion

Implosion starts the client at the top of the hierarchy, not the bottom. The therapist asks them to imagine their most frightening scenario straight away, adding vivid verbal detail to intensify it, a technique called stimulus augmentation.

Nothing happens in the real world. Only the mental picture grows more vivid as the therapist keeps describing it, while the client stays seated throughout.

Two mechanisms are thought to drive the change:

• Exhaustion: Held at a peak for long enough, anxiety triggers physical exhaustion (stimulus satiation), so it can only fall.
• Blocked escape: Preventing the usual avoidance response allows extinction, the weakening of a learned fear once the feared stimulus causes no harm. Yates (1970) called this “forced reality testing”.

This is a world away from Wolpe’s gentle, client-paced hierarchy, and a much harder session to sit through.

Flooding

Flooding works the same way but takes place in real life rather than imagination. A claustrophobic client might be confined in a small space; a flight-phobic client might board an actual aircraft.

The evidence favours it. Four findings stand out:

• Flooding trial: Marks et al. (1971) compared flooding directly with systematic desensitization and found flooding superior.
• Implosion trial: Gelder et al. (1973) found no real difference between implosion and systematic desensitization.
• Review: A review of flooding studies called it the most universally effective phobia treatment available (Marks, 1981).
• Agoraphobia: Emmelkamp and Wessels (1975) and Marks (1981) reported similar success, with gains holding for up to nine years.

Real exposure seems to matter most.

No new symptom replaced the phobia in that time. That answers the old psychodynamic worry about symptom substitution: the idea that removing a symptom just relocates the problem.

Flooding is intensely distressing, sometimes provoking real panic in the client. Stopping a session before anxiety subsides can strengthen the very phobia it aims to cure.

It is used only rarely today. Because it shows exposure alone can work, flooding reshaped how psychologists think about therapy: most contemporary exposure work now drops Wolpe’s insistence on paired relaxation.

Critical Evaluation

Practical Issues

Working with images removes many of the practical barriers to in vivo exposure for this type of phobia.

One weakness of in vitro exposure is that it relies on the client’s ability to imagine the fearful situation.

Some people cannot create a vivid image, and thus, systematic desensitization is not always effective (there are individual differences).

Systematic desensitization is a slow process, taking 6-8 sessions on average. However, research suggests that the longer the technique takes, the more effective it is.

The progressive structure of systematic desensitization allows the patient to control the steps he/she must make until fear is overcome.

This gentler process makes clients less likely to abandon therapy.

Theoretical Issues

Systematic desensitization is highly effective where the problem is learned anxiety of specific objects/situations, e.g., phobias (McGrath et al., 1990).

However, systematic desensitization is not effective in treating serious mental disorders like depression and schizophrenia.

Studies have shown that neither relaxation nor hierarchies are necessary and that the important factor is just exposure to the feared object or situation.

Systematic desensitization is based on the idea that abnormal behavior is learned. The biological approach would disagree and say we are born with a behavior, and therefore it must be treated medically.

Systematic desensitization treats the observable, measurable symptoms of a phobia, not its causes.

This is a real weakness. Cognitions and emotions often drive behavior, so treating only the symptoms leaves the deeper causes untouched.

Social phobias and agoraphobia do not seem to show as much improvement. Other causes may be at work. Perhaps their fears are not simple conditioned associations to a single cue.

Consider a fear of public speaking that originates in poor social skills. A treatment that teaches effective social skills is more likely to reduce the phobia than systematic desensitization alone.

Is Relaxation Necessary?

Researchers discovered that pairing an incompatible response (like relaxation) with the feared stimulus was not actually necessary to reduce anxiety. Wilson and Davison (1971) suggested relaxation may simply be a convenient device that persuades a frightened person to face what they would otherwise avoid.

Instead, prolonged exposure to the stimulus itself drove the change. The client experienced the fear until it naturally subsided (habituation), or learned the stimulus was safe (inhibitory learning).

Marks (1973) reached the same conclusion. Desensitization works through continued exposure until anxiety and avoidance responses are extinguished, not through reciprocal inhibition.

Extinction does not erase the original fear, however. Bouton (2004) reviewed evidence that it adds new, context-dependent learning, which helps explain why fear can return after apparently successful therapy.

Empirical Evidence

Lang and Lazovik (1963) used systematic desensitization with a group of college students who were all suffering from snake phobia. They underwent 11 sessions to work through a hierarchy.

Hypnosis was used to assist in the maintenance of relaxation. The participants’ fear ratings fell, and improvements were still evident six months later.

Rothbaum et al. (2000) treated participants who were afraid of flying with virtual reality exposure, a computer-based form of desensitization. Afterwards, 93% agreed to take a trial flight.

Their anxiety was lower than that of an untreated control group. The improvement was still present at a six-month follow-up.

The untreated control group and the mix of self-report and physiological measures give reasonable confidence that SD, not the passage of time, produced the improvement. Recruiting real sufferers through a media campaign adds real-world relevance.

The main weakness is the missing follow-up. Unlike Lang and Lazovik (1963) and Rothbaum et al. (2000), the study cannot show whether the gains lasted, so some of the treated group may have relapsed.

Contemporary Research

Craske et al. (2014) reframed what makes exposure work. Older approaches, including SD, aimed to lower anxiety within a session. Craske argues the real mechanism is different: the client builds a new “the feared outcome will not happen” memory that competes with the old fear association, called inhibitory learning.

This shifts what good practice looks like. Craske recommends violating the client’s expectations, varying the situations practised, and dropping safety behaviours, rather than sticking to a strict, gentle order.

Virtual reality has become a mainstream tool for exposure work. Rothbaum et al. (2000) pioneered it for fear of flying.

VR headsets let a client face a controllable, repeatable version of a spider, a height or a flight. It offers much of the realism of in vivo exposure without the practical difficulties.

A large meta-analysis supports the approach. Carl et al. (2019) pooled 30 randomized controlled trials with 1,057 participants, covering specific phobias, social and performance anxiety, PTSD and panic disorder.

Virtual reality exposure clearly beat a waitlist control (g = 0.90). It did not differ significantly from in vivo exposure (g = −0.07).

Alternatives to Systematic Desensitization

Systematic desensitization is the historical parent of modern graded exposure, which is often delivered as the exposure component of cognitive behavioral therapy. Several alternatives now compete with it:

• Flooding and implosion: Expose the client to the most feared stimulus at once, without relaxation or a hierarchy.
• Modelling: The client watches a model handle the feared object calmly, then imitates it (social learning theory).
• Cognitive behavioral therapy: Adds work on the beliefs and predictions that sustain anxiety, usually with graded exposure built in.
• Exposure and response prevention: The treatment of choice for OCD, it exposes the client to triggers while blocking the compulsive response.
• Mindfulness-based approaches: Teach clients to observe and accept anxious sensations without judgment, rather than relax them away.

Ethical Issues

Systematic desensitization increases the client’s sense of self-control: the therapist suggests, guides and helps, without controlling the process.

This technique thus minimizes the risk of dependence on the therapist, or of crediting improvement to something external.

The contrast with flooding is stark. Flooding deliberately induces extreme anxiety, and some clients emerge more fearful or even need hospital care. Ending a session before the anxiety subsides can strengthen the phobia, so critics question whether flooding is acceptable at all.

References

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