Caffeine-induced anxiety disorder is a subclass of the DSM-5 diagnosis of substance/medication-induced anxiety disorder. [1]
Consumption of caffeine has long been linked to anxiety. [2] The effects of caffeine and the symptoms of anxiety both increase activity within the sympathetic nervous system. Caffeine has been linked to the aggravation and maintenance of anxiety disorders, and the initiation of panic or anxiety attacks in those who are already predisposed to such phenomena. [3] Caffeine usage surpassing 400 mg has been shown to increase the likelihood for anxiety and panic attacks in a population. Individuals with panic attack disorder have a higher risk of developing a panic attack when consuming caffeine than when they do not. [4] Excessive amounts of caffeine can result in symptoms from general anxiety to obsessive-compulsive and phobic symptoms.
Caffeine-induced anxiety disorder is a subclass of the DSM-5 diagnosis of substance/medication-induced anxiety disorder. The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, or DSM-5, is the current authority for psychiatric diagnosis in the United States. Substance/medication-induced anxiety disorder falls under the category of anxiety disorders in the DSM-5, and not the category of substance-related and addictive disorders, even though the symptoms are due to the effects of a substance. [5]
Diagnosis according to the DSM-5 is dependent on various criteria. Patients must present symptoms of either panic attacks or anxiety. There must also be evidence that the panic or anxiety symptoms are a direct result of the use of the intoxicating substance. In caffeine-induced anxiety disorder, such symptoms would be due to the consumption of caffeine. The DSM-5 makes the distinction that the substance must be physiologically capable of leading to the anxiety and panic symptoms. This establishes the relationship between the abused chemical agent and the observed clinical effects. Caffeine has been proven to act as an antagonist on adenosine receptors, which acts as a stimulant and therefore fulfills this criterion. Symptoms must also not have a more likely clinical cause, such as another type of anxiety disorder, come before the ingestion of the intoxicating substance, or last for an extended amount of time after stopping the use of the substance. Diagnosis also requires that the panic attacks or anxiety due to the use of the intoxicating substance cause a certain amount of disturbance in the patient or lead to deficiency of varying types of daily performance. [5]
In addition to the criteria above, it is important to recognize that the diagnostic criteria for substance/medication-induced anxiety disorder are not met if the symptoms of panic come before the intoxication by the substance. In caffeine-induced anxiety disorder, a diagnosis will not be made if symptoms of anxiety or panic precede the ingestion of caffeine. Also, if symptoms persist for more than one month after substance intoxication, the diagnosis cannot be made. Persistence and continuation of symptoms beyond the initial consumption of caffeine suggest an alternate diagnosis that would better explain the long-lasting symptoms. Anxiety symptoms caused by caffeine are often mistaken for serious mental disorders including bipolar disorder and schizophrenia, leaving patients medicated for the wrong issue. [6] A caffeine-induced anxiety disorder diagnosis should be made, rather than a substance abuse or intoxication diagnosis, when symptoms of panic attacks or anxiety predominate. [7]
Although exact rates of prevalence are not available, general population data shows a 0.002% prevalence over a year-long period and higher prevalence within clinical populations. [7]
Caffeine is a methylxanthine, and is hydrophobic. [8] The structure of caffeine allows the molecule to pass freely through biological membranes including the blood-brain barrier. Absorption in the gastrointestinal tract reaches near completion at about 99% after only 45 minutes. Half-life of caffeine for most adults is between 2.5 and 4.5 hours when consumption is limited to less than 10 mg/kg. However, during neonatal development, half-life for the fetus is significantly longer and decreases exponentially after birth to reach a normal rate at about 6 months. [8] Cytochrome P-450, a hemeprotein, acts in liver microsomes to metabolize caffeine into dimethylxanthines, monomethylxanthines, dimethyl uric acids, monomethyl uric acids, trimethylallantoin, dimethylallantoin, and derivatives of uracil. Most caffeine is metabolized by 3-methyl demethylation, forming the metabolite of paraxanthine. Many metabolites, in addition to caffeine, act within the body and are partly responsible for the physiological response to caffeine. [8]
Caffeine acts in multiple ways within the brain and the rest of the body. However, due to the concentration of caffeine required, antagonism of adenosine receptors is the primary mode of action. [9] The following mechanisms are ways in which caffeine may act within the body, but depending on necessary caffeine concentration and other factors may not be responsible for the clinical effects of the substance.
At very high concentrations of about 1–2 mM, caffeine lowers the excitability threshold in muscle cells, leading to prolonged contraction. The introduction of such high doses of caffeine allows calcium to enter the muscle cell through the plasma membrane and sarcoplasmic reticulum more readily. Influx of calcium through the membranes in muscle cells requires at least 250 μM of caffeine. Normally, other toxic effects of caffeine begin to occur in concentrations over 200 μM, however average consumption averages lead to concentrations less than 100 μM. This means that calcium influx and mobilization are most likely not the cause of caffeine's effect on the central nervous system, and are therefore not the cause of caffeine-induced anxiety disorder. [9]
Methylxanthines such as caffeine inhibit the action of cyclic nucleotide phosphodiesterase, which normally acts to break down cAMP. Cyclic adenosine monophosphate, or cAMP, is a second messenger important in many cellular processes and is a critical factor in signal transduction. The inhibition of the phosphodiesterase would lead to a buildup of cAMP, increasing the activity of the second messenger throughout the cell. Though this mechanism is possible, it only occurs after levels of caffeine have reached a toxic level, and therefore it is unlikely to explain the mechanism of caffeine in the brain. [9]
There are four well-known adenosine receptors found in the body, A1, A2A, A2B, and A3. The endogenous agonist for these receptors is adenosine, which is a purine nucleoside that is important for processes such as energy transfer in the form of adenosine triphosphate (ATP) and adenosine monophosphate (AMP) and signal transduction in the form of cyclic adenosine monophosphate (cAMP). A2B and A3 receptors require concentrations of caffeine that do not occur at normal physiological levels or with normal levels of caffeine consumption in order to be antagonized, and will therefore not be considered as a possible mechanism for caffeine-induced anxiety. [8]
Caffeine acts as an antagonist of adenosine A1 and A2A receptors. Adenosine is a normal neuromodulator that activates adenosine g-protein coupled receptors. The actions of A1 and A2A receptors oppose each other but are both inhibited by caffeine due to its function as an antagonist. [8]
A2A receptors are coupled to Gs proteins which activate adenylate cyclase and some voltage gated Ca2+ channels. A2A receptors are located in dopamine rich brain regions. A2A receptor mRNA was found in the same neurons as the dopamine receptor D2 within the dorsal striatum, nucleus accumbens and tuberculum olfactorium. A2A receptors are not found in neurons that express the dopamine receptor D1 receptors and Substance P. Within the striatum, part of the basal ganglia, activation of A2A receptors by adenosine increases GABA release, an inhibitory neurotransmitter. When caffeine binds to the receptor, less inhibitory neurotransmitter is released, supporting caffeine's role as a central nervous system stimulant. [8]
A1 receptors are paired with the G-proteins of Gi-1, Gi-2, Gi-3, Go1, and Go2. The g-proteins of A1 receptors continue to inhibit adenylate cyclase, some voltage gated Ca2+ channels, and activate some K+ channels, and phospholipase C and D. A1 receptors are primarily located in the hippocampus, cerebral and cerebellar cortex, and particular thalamic nuclei. Adenosine acts on A1 receptors to decrease opening of N-type Ca2+ channels in some hippocampal neurons, and therefore decrease the rate of firing since Ca2+ is necessary for neurotransmitter release. Caffeine's antagonistic action on the A1 receptor thus decreases the action of adenosine, allowing increased Ca2+ entry through N-type channels and higher rates of neurotransmitter release. [8]
Though antagonism of adenosine receptors is the primary mechanism of caffeine, Introduction of the methylxanthine into the body also increases the rate of release and recycling of some monoamine neurotransmitters such as noradrenaline and dopamine. Caffeine also has an excitatory effect on mesocortical cholinergic neurons by acting as an antagonist on adenosine receptors that normally inhibit the neuron. [8]
While many factors contribute to individual differences in a person's response to caffeine, such as environmental and demographic factors (i.e. age, drug use, circadian factors, etc.), genetics play an important role in individual variability. This inconsistency in responses to caffeine can take place either at the metabolic or at the drug-receptor level. [7] The effects of genetic factors can occur either directly by changing acute or chronic reactions to the drug or indirectly by altering other psychological or physiological processes. [7]
Some of these processes include wakefulness, stimulation, and mood and cognition enhancement. Low doses can result in psychological effects of "mild euphoria, alertness, and enhanced cognitive performance"; [7] higher doses produce physiological side effects of nausea, anxiety, trembling, and jitteriness.
There are individuals who are prone to caffeine's anxiogenic effects whilst others are susceptible to its caffeine-induced sleep disturbances and insomnia. Studies with twins have shown that genetics influence individual differences in response to caffeine. Homozygous twins have been found to react in more consistent ways to the caffeine than heterozygous twins. [9]
Caffeine's widespread appeal is due primarily to its mild psychostimulant properties, which increase alertness and cognitive arousal and diminish fatigue. [10] Caffeine also produces a wide range of other symptoms, including upregulation of the cardiovascular system, increased global cognitive processing, and improved physical functioning. Cardiovascular effects can range from increased heart rate and reactivity to severe cardiac arrhythmia. [10] The cognitive effects of caffeine include increased performance in memory, attention, and text reading. [11] The physical effects of caffeine include lowered sensations of pain, less perceived effort, and increased muscle strength and endurance. However, at doses above ~400 mg, both cognitive and physical performance begins to worsen and symptoms of anxiety increase. [12] One study that explored ad lib caffeine consumption in 159 college students found that high consumers reported lower academic performance. The same study also concluded that moderate and high consumers combined reported significantly higher trait anxiety and depression scores when compared with abstainers. [13] These anxiety symptoms include persisting insomnia, nervousness, and mood fluctuations. [10]
When undergoing stress, the body activates a system-wide response mechanism known as the HPA axis. This stress signal begins at the level of the hypothalamus in the brain and undergoes subsequent amplifications throughout the body. This system elevates levels of stress hormones in the blood, which results in the body shutting down secondary bodily processes and increasing alertness to better prepare for response to the perceived threat. [14] Studies show that activation of this pathway is correlated with anxiety-like behaviors, including panic, post-traumatic stress, and generalized anxiety disorders, [15] [16] as well as depression. [17] Rodent studies show that caffeine consumption in adolescence results in dysregulation of HPA axis function as well as central nervous system response, which impairs the body's response to stressful stimuli. [18]
In cases of prolonged consumption of excess amounts of caffeine, studies show that individuals exhibit a reduced response to HPA axis activation by the hormone ACTH and a generalized increase in basal levels of stress hormone corticosterone. Researchers concluded that the sensitivity of adrenal glands to ACTH is diminished by caffeine consumption. People diagnosed with panic disorder show less HPA activity following stressful stimuli than their healthy control counterparts. [18]
Caffeine has varying effects on anxiety across given populations. The populations most susceptible to caffeine-induced anxiety disorder include those already diagnosed with an anxiety disorder and adolescents. Adolescents, particularly, are at increased risk for developing anxiety disorders and anxiety-related symptoms. While few human studies have been done to investigate this connection, many rodent studies show a correlation between caffeine consumption in adolescence and increased anxiety. [18] [19] [20] [21] These studies showed that in adolescent rodents exposed to caffeine, functioning of serotonin systems was affected, leading to increased anxiety; [20] anxiety-related behaviors were higher than in adult rats exposed to the same amount of caffeine; [21] and reward seeking behaviors as well as mood fluctuations were increased as the rodents matured. [19] Rats with high anxiety behavior when exposed to a high dose of caffeine decreased their risk taking as well as the expression of neurite growth signal BDNF in caudate putamen, compared to low anxiety behavior rats. [22]
When consumed in moderation, caffeine can have many beneficial effects. However, over the course of several years, chronic caffeine consumption can produce various long-term health deficits in individuals. Among these, rodent studies have suggested caffeine intake may permanently alter the brain's excitability. [23]
For individuals being treated with benzodiazepines such as alprazolam (Xanax) for anxiety disorders, even small amounts of caffeine may have negative effects on treatment. Caffeine is able to negate the effects of benzodiazepines which can lead to heightened levels of anxiety and even panic attacks. [24] Studies have linked caffeine intake to increased rates of cytotoxicity and cell death by necrosis associated with benzodiazepine use. [25] However, this phenomenon (thought to be mediated via TSPO) is also present with benzodiazepine use alone. The clinical significance of caffeine-benzodiazepine induced cytotoxicity in humans is unclear and has not been shown to be harmful. [26] [27] Although benzodiazepines are effective at managing acute caffeine-induced anxiety symptoms, avoiding caffeine is generally recommended rather than increasing benzodiazepine intake. Treatments for caffeine-induced anxiety disorder tend to focus on abstinence from or a reduction of caffeine intake and behavioral therapy. [24] Some doctors may recommend a continuance of caffeine consumption but with the provision that the patient actively takes note of physiological changes that happen after caffeine intake. The goal of this approach is to help patients better understand the effects of caffeine on the body and to distinguish threatening symptoms from normal reactions. [28]
Anxiety is an emotion which is characterised by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different from fear in that fear is defined as the emotional response to a present threat, whereas anxiety is the anticipation of a future one. It is often accompanied by nervous behavior such as pacing back and forth, somatic complaints, and rumination.
Benzodiazepines, colloquially known as "benzos", are a class of depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat conditions such as anxiety disorders, insomnia, and seizures. The first benzodiazepine, chlordiazepoxide (Librium), was discovered accidentally by Leo Sternbach in 1955, and was made available in 1960 by Hoffmann–La Roche, which followed with the development of diazepam (Valium) three years later, in 1963. By 1977, benzodiazepines were the most prescribed medications globally; the introduction of selective serotonin reuptake inhibitors (SSRIs), among other factors, decreased rates of prescription, but they remain frequently used worldwide.
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class and is the most commonly consumed psychoactive substance globally. It is mainly used for its eugeroic, ergogenic, or nootropic properties. Caffeine acts by blocking binding of adenosine at a number of adenosine receptor types, inhibiting the centrally depressant effects of adenosine and enhancing the release of acetylcholine. Caffeine has a three-dimensional structure similar to that of adenosine, which allows it to bind and block its receptors. Caffeine also increases cyclic AMP levels through nonselective inhibition of phosphodiesterase, increases calcium release from intracellular stores, and antagonises GABA receptors, although these mechanisms typically occur at concentrations beyond usual human consumption.
Psychopharmacology is the scientific study of the effects drugs have on mood, sensation, thinking, behavior, judgment and evaluation, and memory. It is distinguished from neuropsychopharmacology, which emphasizes the correlation between drug-induced changes in the functioning of cells in the nervous system and changes in consciousness and behavior.
A mood disorder, also known as an affective disorder, is any of a group of conditions of mental and behavioral disorder where the main underlying characteristic is a disturbance in the person's mood. The classification is in the Diagnostic and Statistical Manual of Mental Disorders (DSM) and International Classification of Diseases (ICD).
Agoraphobia is a mental and behavioral disorder, specifically an anxiety disorder characterized by symptoms of anxiety in situations where the person perceives their environment to be unsafe with no easy way to escape. These situations can include public transit, shopping centers, crowds and queues, or simply being outside their home on their own. Being in these situations may result in a panic attack. Those affected will go to great lengths to avoid these situations. In severe cases, people may become completely unable to leave their homes.
Panic attacks are sudden periods of intense fear and discomfort that may include palpitations, otherwise defined as a fluttering, rapid, irregular heartbeat, sweating, chest pain or chest discomfort, shortness of breath, trembling, dizziness, numbness, confusion, or a sense of impending doom or loss of control. Typically, these symptoms peak within ten minutes of onset and can last for roughly 30 minutes, though their duration can vary anywhere from seconds to even hours. While they can be extremely frightening and distressing, panic attacks themselves are not physically dangerous.
Depersonalization is a dissociative phenomenon characterized by a subjective feeling of detachment from oneself, manifesting as a sense of disconnection from one's thoughts, emotions, sensations, or actions, and often accompanied by a feeling of observing oneself from an external perspective. Subjects perceive that the world has become vague, dreamlike, surreal, or strange, leading to a diminished sense of individuality or identity. Sufferers often feel as though they are observing the world from a distance, as if separated by a barrier "behind glass". They maintain insight into the subjective nature of their experience, recognizing that it pertains to their own perception rather than altering objective reality. This distinction between subjective experience and objective reality distinguishes depersonalization from delusions, where individuals firmly believe in false perceptions as genuine truths. Depersonalization is also distinct from derealization, which involves a sense of detachment from the external world rather than from oneself.
The adenosine receptors (or P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as the endogenous ligand. There are four known types of adenosine receptors in humans: A1, A2A, A2B and A3; each is encoded by a different gene.
Hallucinogen persisting perception disorder (HPPD) is a non-psychotic disorder in which a person experiences apparent lasting or persistent visual hallucinations or perceptual distortions after using drugs, including but not limited to psychedelics, dissociatives, entactogens, tetrahydrocannabinol (THC), and SSRIs. Despite being designated as a hallucinogen-specific disorder, the specific contributory role of psychedelic drugs is unknown.
Caffeine dependence is a condition characterized by a set of criteria, including tolerance, withdrawal symptoms, persistent desire or unsuccessful efforts to control use, and continued use despite knowledge of adverse consequences attributed to caffeine. It can appear in physical dependence or psychological dependence, or both. Caffeine is one of the most common additives in many consumer products, including pills and beverages such as caffeinated alcoholic beverages, energy drinks, pain reliever medications, and colas. Caffeine is found naturally in various plants such as coffee and tea. Studies have found that 89 percent of adults in the U.S. consume on average 200 mg of caffeine daily. One area of concern that has been presented is the relationship between pregnancy and caffeine consumption. Repeated caffeine doses of 100 mg appeared to result in smaller size at birth in newborns. When looking at birth weight however, caffeine consumption did not appear to make an impact.
An anxiogenic or panicogenic substance is one that causes anxiety. This effect is in contrast to anxiolytic agents, which inhibits anxiety. Together these categories of psychoactive compounds may be referred to as anxiotropic compounds.
Caffeine-induced sleep disorder was a psychiatric disorder identified as resulting from overconsumption of the stimulant caffeine.
Dual diagnosis is the condition of having a mental illness and a comorbid substance use disorder. There is considerable debate surrounding the appropriateness of using a single category for a heterogeneous group of individuals with complex needs and a varied range of problems. The concept can be used broadly, for example depression and alcohol use disorder, or it can be restricted to specify severe mental illness and substance use disorder, or a person who has a milder mental illness and a drug dependency, such as panic disorder or generalized anxiety disorder and is dependent on opioids. Diagnosing a primary psychiatric illness in people who use substances is challenging as substance use disorder itself often induces psychiatric symptoms, thus making it necessary to differentiate between substance induced and pre-existing mental illness.
SCH-58261 is a drug which acts as a potent and selective antagonist for the adenosine receptor A2A, with more than 50x selectivity for A2A over other adenosine receptors. It has been used to investigate the mechanism of action of caffeine, which is a mixed A1 / A2A antagonist, and has shown that the A2A receptor is primarily responsible for the stimulant and ergogenic effects of caffeine, but blockade of both A1 and A2A receptors is required to accurately replicate caffeine's effects in animals. SCH-58261 has also shown antidepressant, nootropic and neuroprotective effects in a variety of animal models, and has been investigated as a possible treatment for Parkinson's disease.
Post-acute withdrawal syndrome (PAWS) is a hypothesized set of persistent impairments that occur after withdrawal from alcohol, opiates, benzodiazepines, antidepressants, and other substances. Infants born to mothers who used substances of dependence during pregnancy may also experience a PAWS. While PAWS has been frequently reported by those withdrawing from opiate and alcohol dependence, the research has limitations. Protracted benzodiazepine withdrawal has been observed to occur in some individuals prescribed benzodiazepines.
Psychological dependence is a cognitive disorder and a form of dependence that is characterized by emotional–motivational withdrawal symptoms upon cessation of prolonged drug use or certain repetitive behaviors. Consistent and frequent exposure to particular substances or behaviors is responsible for inducing psychological dependence, requiring ongoing engagement to prevent the onset of an unpleasant withdrawal syndrome driven by negative reinforcement. Neuronal counter-adaptation is believed to contribute to the generation of withdrawal symptoms through changes in neurotransmitter activity or altered receptor expression. Environmental enrichment and physical activity have been shown to attenuate withdrawal symptoms.
Istradefylline, sold under the brand name Nourianz, is a medication used as an add-on treatment to levodopa/carbidopa in adults with Parkinson's disease (PD) experiencing "off" episodes. Istradefylline reduces "off" periods resulting from long-term treatment with the antiparkinson drug levodopa. An "off" episode is a time when a patient's medications are not working well, causing an increase in PD symptoms, such as tremor and difficulty walking.
Benzodiazepine dependence defines a situation in which one has developed one or more of either tolerance, withdrawal symptoms, drug seeking behaviors, such as continued use despite harmful effects, and maladaptive pattern of substance use, according to the DSM-IV. In the case of benzodiazepine dependence, the continued use seems to be typically associated with the avoidance of unpleasant withdrawal reaction rather than with the pleasurable effects of the drug. Benzodiazepine dependence develops with long-term use, even at low therapeutic doses, often without the described drug seeking behavior and tolerance.
Panic disorder is a mental and behavioral disorder, specifically an anxiety disorder characterized by reoccurring unexpected panic attacks. Panic attacks are sudden periods of intense fear that may include palpitations, sweating, shaking, shortness of breath, numbness, or a feeling that something terrible is going to happen. The maximum degree of symptoms occurs within minutes. There may be ongoing worries about having further attacks and avoidance of places where attacks have occurred in the past.