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Research on Child and Adolescent Psychopathology
Gepubliceerd in:

01-02-2010

Relations Among Perceived Control Over Anxiety-Related Events, Worry, and Generalized Anxiety Disorder in a Sample of Adolescents

Auteurs: Jamie L. Frala, Ellen W. Leen-Feldner, Heidemarie Blumenthal, Carolina C. Barreto

Gepubliceerd in: Research on Child and Adolescent Psychopathology | Uitgave 2/2010

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Abstract

This study examined the associations among perceived control over anxiety-related events, worry, and both symptoms and diagnoses of generalized anxiety disorder (GAD). The sample was comprised of 140 adolescents (60 girls) between the ages of 10 and 17 years (M age  = 14.6 years; SD = 2.25) recruited from the general community. Findings were consistent with hypotheses. Self-reported perceived control over anxiety-related events related negatively to worry as well as symptoms and diagnoses of GAD even after accounting for variance associated with age, gender, and negative affectivity. Results are discussed in terms of the theoretical implications that perceived control over anxiety-related events may have for understanding GAD symptomatology among youth.
vorige artikel Vigilance and Avoidance of Threat in the Eye Movements of Children with Separation Anxiety Disorder
volgende artikel A Psychometric Analysis of the Revised Child Anxiety and Depression Scale—Parent Version in a Clinical Sample
Voetnoten
1
Regression analyses were also conducted excluding individuals with GAD; the pattern and magnitude of the results was unchanged.
 
Literatuur
Abel, J. L., & Borkovec, T. D. (1995). Generalizability of DSM-III-R generalized anxiety disorder to proposed DSM-IV criteria and cross validation of proposed changes. Journal of Anxiety Disorders, 9, 303–315.CrossRef
Alloy, L. B., Kelly, K. A., Mineka, S., & Clements, C. M. (1990). Comorbidity of anxiety and depressive disorders: a helplessness-hopelessness perspective. In J. D. Maser & R. C. Cloninger (Eds.), Comorbidity of mood and anxiety disorders (pp. 499–543). Washington: American Psychiatric Association.
American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington: Author.
American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed. Text Revision). Washington: Author.
Arnett, J. J. (2004). Emerging adulthood: The winding road from the late teens through twenties. New York: Oxford University Press.
Ballash, N., Leyfer, O., Buckley, A. F., & Woodruff-Borden, J. (2006). Parental control in the etiology of anxiety. Clinical Child and Family Psychology Review, 9, 113–133.CrossRefPubMed
Bandura, A. (1977). Self-efficacy: toward a unifying theory of behavioral change. Psychological Review, 84, 191–215.CrossRefPubMed
Bandura, A. (1982). Self-efficacy mechanism in human agency. American Psychologist, 37, 122–147.CrossRef
Barahmand, U. (2008). Age and gender differences in adolescent worry. Personality and Individual Differences, 45, 778–783.CrossRef
Barlow, D. H. (2002). Anxiety and its disorders: The nature and treatment of anxiety and panic (2nd ed.). New York: Guilford.
Beck, A. T., & Emery, G. (1985). Anxiety disorders and phobias: A cognitive perspective. New York: Basic Books.
Bonetti, D., & Johnston, M. (2008). Perceived control predicting the recovery of individual-specific walking behaviours following stroke: testing psychological models and constructs. British Journal of Health Psychology, 13, 463–478.CrossRefPubMed
Brown, A. M., & Whiteside, S. P. (2008). Relations among perceived parental rearing behaviors, attachment style, and worry in anxious children. Journal of Anxiety Disorders, 22, 263–272.CrossRefPubMed
Brown, T. A., Chorpita, B. F., & Barlow, D. H. (1998). Structural relationships among dimensions of the DSM-IV anxiety and mood disorders and dimensions of negative affect, positive affect, and autonomic arousal. Journal of Abnormal Psychology, 107, 179–192.CrossRefPubMed
Case, R. (1987). The structure and process of intellectual development. International Journal of Psychology, 22, 571–607.CrossRef
Chorpita, B. F. (2001). Control and the development of negative emotions. In M. W. Vasey & M. R. Dadds (Eds.), The developmental psychopathology of anxiety (pp. 112–142). New York: Oxford University Press.
Chorpita, B. F., & Barlow, D. H. (1998). The development of anxiety: the role of control in the early environment. Psychological Bulletin, 124, 3–21.CrossRefPubMed
Chorpita, B. F., Tracey, S. A., Brown, T. A., Colica, T. J., & Barlow, D. H. (1997). Assessment of worry in children and adolescents: an adaptation of the Penn State worry questionnaire. Behaviour Research and Therapy, 35, 569–581.CrossRefPubMed
Chorpita, B. F., Brown, T. A., & Barlow, D. H. (1998). Perceived control as a mediator of family environment in etiological models of childhood anxiety. Behavior Therapy, 29, 457–476.CrossRef
Chorpita, B. F., Yim, L., Moffitt, C., Umemoto, L. A., & Francis, S. E. (2000). Assessment of symptoms of DSM-IV anxiety and depression in children: a revised child anxiety and depression scale. Behaviour Research and Therapy, 38, 835–855.CrossRefPubMed
Chorpita, B. F., Moffitt, C. E., & Gray, J. (2005). Psychometric properties of the revised child anxiety and depression scale in a clinical sample. Behaviour Research and Therapy, 43, 309–322.CrossRefPubMed
Cicchetti, D., & Rogosch, F. (2002). A developmental psychopathology perspective on adolescence. Journal of Consulting and Clinical Psychology, 70, 6–20.CrossRefPubMed
Clark, L. A., Watson, D., & Mineka, S. (1994). Temperament, personality and the mood and anxiety disorders. Journal of Abnormal Psychology, 103, 103–116.CrossRefPubMed
Cohen, J. (1988). Statistical power analysis for the behavioural sciences (2nd ed.). Hillsdale: Erlbaum.
Coles, M. E., Turk, C. L., & Heimberg, R. G. (2007). Memory bias for threat in generalized anxiety disorder: the potential importance of stimulus relevance. Cognitive Behaviour Therapy, 36, 65–73.CrossRefPubMed
Craske, M. G. (1999). Anxiety disorders: Psychological approaches to theory and treatment. Boulder: Westview.
Craske, M. G., & Hazlett-Stevens, H. (2002). Facilitating symptom reduction and behavior change in GAD: the issue of control. Clinical Psychology: Science and Practice, 9, 69–75.CrossRef
Craske, M. G., Rapee, R. M., Jackel, L., & Barlow, D. H. (1989). Qualitative dimensions of worry in DSM-IIR generalized anxiety disorder subjects and nonanxious controls. Behavior Research and Therapy, 27, 397–402.CrossRef
Davey, G. C. L. (1994). Pathological worrying as exacerbated problem solving. In G. C. L. Davey & F. Tallis (Eds.), Worrying: perspectives on theory, assessment and treatment (pp. 35–59). Chichester: Wiley.
Davey, G. C. L., Tallis, F., & Capuzzo, N. (1996). Beliefs about the consequences of worrying. Cognitive Therapy and Research, 20, 499–520.CrossRef
Feldman, S., & Elliot, G. (Eds.) (1990). At the threshold: The developing adolescent. Cambridge: Harvard University Press.
Feldner, M. T., & Hekmat, H. (2001). Perceived control over anxiety-related events as a predictor of pain behaviors in a cold pressor task. Journal of Behavior Therapy and Experimental Psychiatry, 32, 191–202.CrossRefPubMed
Fisher, K. M. (1985). Elaboration of cognitive knowledge of biology from childhood to adulthood. Journal of General Psychology, 112, 389–397.
Friedman, B. H., Thayer, J. F., & Borkovec, T. D. (2000). Explicit memory bias for threat words in generalized anxiety disorder. Behavior Therapy, 31, 745–756.CrossRef
Gallagher, M., & Miller, R. (1998). Gender and age differences in the concerns of adolescents in Northern Ireland. Adolescence, 33, 863–876.PubMed
Ginsburg, G. S., Lambert, S., & Drake, K. (2004). Attributions of control, anxiety sensitivity, and panic symptoms among adolescents. Cognitive Therapy and Research, 28, 745–763.CrossRef
Golomobok, S., & Fivush, R. (1994). Gender development. Cambridge: Cambridge University Press.
Gosselin, P., Langlois, F., Freeston, M. H., Ladouceur, R., Laberge, M., & Lemay, D. (2007). Cognitive variables related to worry among adolescents: avoidance strategies and faulty beliefs about worry. Behaviour Research and Therapy, 45, 225–233.CrossRefPubMed
Hale, W. W., III, Engels, R., & Meeus, W. (2006). Adolescent’s perceptions of parenting behaviours and its relationship to adolescent generalized anxiety disorder symptoms. Journal of Adolescence, 29, 407–417.CrossRefPubMed
Hayward, C. (Ed.) (2003). Gender differences at puberty. New York: Cambridge University Press.
Hazlett-Stevens, H., & Borkovec, T. D. (2004). Interpretive cues and ambiguity in generalized anxiety disorder. Behaviour Research and Therapy, 42, 881–892.CrossRefPubMed
Helgeson, V. S. (1992). Moderators of the relation between perceived control and adjustment to chronic illness. Journal of Personality and Social Psychology, 63, 656–666.CrossRefPubMed
Hofmann, S. G. (2005). Perception of control over anxiety mediates the relationship between catastrophic thinking and social anxiety in social phobia. Behaviour Research and Therapy, 43, 885–895.CrossRefPubMed
Hogendoorn, S. M., Wolters, L. H., Vervoort, L., Prins, P. J. M., Boer, F., & Haan, E. D. (2008). An indirect and direct measures of anxiety-related perceived control in children: the implicit association procedure (IAP) and anxiety control questionnaire for children (ACQ-C). Journal of Behavior Therapy and Experimental Psychiatry, 39, 436–450.CrossRefPubMed
Jacques, H. A. K., & Mash, E. J. (2004). A test of the tripartite model of anxiety and depression in elementary and high school boys and girls. Journal of Abnormal Child Psychology, 32, 13–25.CrossRefPubMed
Joiner, T. E., Catanzaro, S. J., & Laurent, J. (1996). Tripartite structure of positive and negative affect, depression, and anxiety in child and adolescent psychiatric inpatients. Journal of Abnormal Psychology, 105, 401–409.CrossRefPubMed
Kraemer, H. C., Stice, E., Kazdin, A., Offord, D., & Kupfer, D. (2001). How do risk factors work together? Mediators, moderators, and independent, overlapping, and proxy risk factors. American Journal of Psychiatry, 158, 848–856.PubMed
Landon, T. M., Ehrenreich, J. T., & Pincus, D. B. (2007). Self-efficacy: a comparison between clinically anxious and non-referred youth. Child Psychiatry & Human Development, 38, 31–45.CrossRef
Lang, A. J., & McNiel, D. E. (2006). Use of the anxiety control questionnaire in psychiatric inpatients. Depression and Anxiety, 23, 107–112.CrossRefPubMed
Larson, R. W., Richards, M. H., Moneta, G., Holmbeck, G., & Duckett, E. (1996). Changes in adolescents’ daily interactions with their families from ages 10 to 18: disengagement and transformation. Developmental Psychology, 32, 744–754.CrossRef
Laurent, J., Catanzaro, S. J., Salvatore, J., & Joiner, T. E. (2004). Development and preliminary validation of the physiological hyperarousal scale for children. Psychological Assessment, 16, 373–380.CrossRefPubMed
Leen-Feldner, E. W., Feldner, M. T., Tull, M. T., Roemer, L., & Zvolensky, M. J. (2006). An examination of worry in relation to anxious responding to voluntary hyperventilation among adolescents. Behaviour Research and Therapy, 44, 1803–1809.CrossRefPubMed
Leen-Feldner, E. W., Blumenthal, H., Babson, K., Bunaciu, L., & Feldner, M. T. (2008). Parenting-related childhood learning history and panic vulnerability: a test using a laboratory-based biological challenge procedure. Behaviour Research and Therapy, 46, 1009–1016.CrossRefPubMed
Lyonfields, J. D., Borkovec, T. D., & Thayer, J. F. (1995). Vagal tone in generalized anxiety disorder and the effects of aversive imagery and worrisome thinking. Behavior Therapy, 26, 457–466.CrossRef
MacLeod, C., & Cohen, I. L. (1993). Anxiety and the interpretation of ambiguity: a text comprehension study. Journal of Abnormal Psychology, 102, 238–247.CrossRefPubMed
Magnusson, D., Stattin, H., & Allen, V. L. (1985). Biological maturation and social development: a longitudinal study of some adjustment processes from mid-adolescence to adulthood. Journal of Youth and Adolescence, 14, 267–283.CrossRef
Mathews, A., & MacLeod, C. (1985). Selective processing of threat cues in anxiety states. Behaviour Research and Therapy, 23, 563–569.CrossRefPubMed
McLaughlin, K. A., Borkovec, T. D., & Sibrava, N. J. (2007). The effects of worry and rumination on affect states and cognitive activity. Behavior Therapy, 38, 23–38.CrossRefPubMed
Mennin, D. S., Heimberg, R. G., Turk, C. L., & Fresco, D. M. (2002). Applying an emotion regulation framework to integrative approaches to generalized anxiety disorder. Clinical Psychology: Science and Practice, 9, 85–90.CrossRef
Mineka, S., & Hendersen, R. W. (1985). Controllability and predictability in acquired motivation. Annual Review of Psychology, 36, 495–529.CrossRefPubMed
Mineka, S., & Kelly, K. (1989). The relationship between anxiety, lack of control, and loss of control. In A. Steptoe & A. Appels (Eds.), Stress, personal control and health (pp. 163–191). New York: Wiley.
Mineka, S., Gunnar, M., & Champoux, M. (1986). Control and early socioemotional development: infant rhesus monkeys reared in controllable versus uncontrollable environments. Child Development, 57, 1241–1256.CrossRef
Moulding, R., & Kyrios, M. (2006). Anxiety disorders and control related beliefs: the exemplar of obsessive-compulsive disorder (OCD). Clinical Psychology Review, 26, 573–583.CrossRefPubMed
Moulding, R., & Kyrios, M. (2007). Desire for control, sense of control, and obsessive-compulsive symptoms. Cognitive Therapy and Research, 31, 759–772.CrossRef
Muris, P., Meesters, C., Merckelbach, H., & Hülsenbeck, P. (2000). Worry in children is related to perceived parental rearing and attachment. Behaviour Research and Therapy, 38, 487–497.CrossRefPubMed
Muris, P., Meesters, C., & Gobel, M. (2001). Reliability, validity, and normative data of the Penn State worry questionnaire in 8–12-yr-old-children. Journal of Behavior Therapy and Experimental Psychiatry, 32, 63–72.CrossRefPubMed
Muris, P., Meesters, G., Schouten, E., & Hoge, E. (2004). Effects of perceived control on the relationship between perceived parental rearing behaviors and symptoms of anxiety and depression in nonclinical preadolescents. Journal of Youth and Adolescence, 33, 51–58.CrossRef
Nisbett, R., & Ross, L. (1980). Human inference: Strategies and shortcomings of social judgment. Englewood Cliffs: Prentice Hall.
Nolen-Hoeksema, S., Girgus, J. S., & Seligman, M. E. (1992). Predictors and consequences of childhood depressive symptoms: a 5-year longitudinal study. Journal of Abnormal Psychology, 101, 405–422.CrossRefPubMed
Nunn, G. D. (1988). Concurrent validity between the Nowicki–Strickland locus of control scale and the state-trait anxiety inventory for children. Educational and Psychological Measurement, 48, 435–438.CrossRef
Olatunji, B. O., Schottenbauer, M. A., Rodriguez, B. F., Glass, C. R., & Arnkoff, D. B. (2007). The structure of worry: relations between positive/negative personality characteristics and the Penn State worry questionnaire. Journal of Anxiety Disorders, 21, 540–553.CrossRefPubMed
Piaget, J. (1970). Piaget’s theory. In P. H. Mussen (Ed.), Carmichael’s manual of child psychology (Vol. 1, pp. 703–732). New York: Wiley.
Pomerantz, E. M., & Ruble, D. N. (1998). The role of maternal control in the development of sex differences in child self-evaluative factors. Child Development, 69, 458–478.PubMed
Rapee, R. M., Craske, M. G., Brown, T. A., & Barlow, D. H. (1996). Measurement of perceived control over anxiety-related events. Behavior Therapy, 27, 279–293.CrossRef
Reynolds, C. R., & Richmond, B. O. (1978). What I think and feel: a revised measure of the children’s manifest anxiety scale. Journal of Abnormal Child Psychology, 6, 280–297.CrossRef
Roemer, L., & Orsillo, S. M. (2005). An acceptance-based behavior therapy for generalized anxiety disorder. In S. M. Orsillo & L. Roemer (Eds.), Acceptance and mindfulness-based approaches to anxiety: Conceptualization and treatment (pp. 213–240). New York: Springer Science + Business Media.CrossRef
Roemer, L., & Orsillo, S. M. (2007). An open trial of an acceptance-based behavior therapy for generalized anxiety disorder. Behavior Therapy, 38, 72–85.CrossRefPubMed
Rotter, J. B. (1966). Generalized expectancies for internal versus external control of reinforcement. Psychological Monographs, 80. (Whole No. 609).
Sanderson, W. C., Rapee, R. M., & Barlow, D. H. (1989). The influence of an illusion of control on panic attacks induced via the inhalation of 5.5% carbon dioxide enriched air. Archives of General Psychiatry, 46, 1047–1051.
Sechrest, L. (1963). Incremental validity: a recommendation. Educational & Psychological Measurement, 23, 153–158.CrossRef
Seligman, M. E. P. (1975). Helplessness: On depression, development, and death. San Francisco: Freeman.
Shear, K. M. (1991). The concept of uncontrollability. Psychological Inquiry, 2, 88–93.CrossRef
Siegler, R. S. (1983). Five generalizations about cognitive development. American Psychologist, 38, 263–277.CrossRef
Siegler, R. S. (1994). Cognitive variability: a key to understanding cognitive development. Current Directions in Psychological Science, 3, 1–5.CrossRef
Silverman, W. K., & Albano, A. M. (1996). The anxiety disorders interview schedule for DSM-IV: Child and parent versions. San Antonio: Psychological Corporation.
Silverman, W. K., Saavedra, L. M., & Pina, A. A. (2001). Test-retest reliability of anxiety symptoms and diagnoses with anxiety disorders interview schedule for DSM-IV: child and parent versions. Journal of the American Academy of Child and Adolescent Psychiatry, 40, 937–944.CrossRefPubMed
St-Yves, A., Dompierre, S., Freeston, M. H., Jacques, C., & Malo, M. (1989). Locus of control and anxiety in children from intact and maritally disrupted families. Psychological Reports, 65, 855–860.PubMed
Taghavi, M. R., Dalgleish, T., Moradi, A. R., Neshat-Doost, H. T., & Yule, W. (2003). Selective processing of negative emotional information in children and adolescents with generalized anxiety disorder. British Journal of Clinical Psychology, 42, 221–230.CrossRefPubMed
Thienemann, M., Moore, P., & Tompkins, K. (2006). A parent-only group intervention for children with anxiety disorders: pilot study. Journal of the American Academy of Child & Adolescent Psychiatry, 45, 37–46.CrossRef
Thompson, S. C., Sobolew-Shubin, A., Galbraith, M. E., Schwankovsky, L., & Cruzen, D. (1993). Maintaining perceptions of control: finding perceived control in low-control circumstances. Journal of Personality and Social Psychology, 64, 293–304.CrossRefPubMed
U.S. Bureau of the Census. (1997). Statistical abstracts of the United States: 1997. Washington: U.S. Bureau of the Census.
Vasey, M. W., Crnic, K. A., & Carter, W. G. (1994). Worry in childhood: a developmental perspective. Cognitive Therapy and Research, 18, 529–549.CrossRef
Waters, A. M., Mogg, K., Bradley, B. P., & Pine, D. S. (2008). Attentional bias for emotional faces in children with generalized anxiety disorder. Journal of the American Academy of Child & Adolescent Psychiatry, 47, 435–442.CrossRef
Watt, M. C., Stewart, S. H., & Cox, B. J. (1998). A retrospective study of the learning history origins of anxiety sensitivity. Behaviour Research & Therapy, 36, 505–525.CrossRef
Weems, C. F. (2006). Manual for the anxiety control questionnaire for children-short report version. Author: University of New Orleans.
Weems, C. F., & Silverman, W. K. (2006). An integrative model of control: implications for understanding emotion regulation and dysregulation in childhood anxiety. Journal of Affective Disorders, 91, 113–124.CrossRefPubMed
Weems, C. F., Silverman, W. K., Rapee, R. M., & Pina, A. A. (2003). The role of control in childhood anxiety disorders. Cognitive Therapy and Research, 27, 557–568.CrossRef
Weems, C. F., Costa, N. M., Watts, S. E., Taylor, L. K., & Cannon, M. F. (2007). Cognitive errors, anxiety sensitivity, and anxiety control beliefs: their unique and specific association with childhood anxiety symptoms. Behavior Modification, 31, 174–201.CrossRefPubMed
Wood, J. J., Piacentini, J. C., Bergman, R. L., McCracken, J., & Barrios, V. (2002). Concurrent validity of the anxiety disorders section of the anxiety disorders interview schedule for DSM-IV: child and parent versions. Journal of Clinical Child and Adolescent Psychology, 31, 335–342.PubMed
Zvolensky, M. J., Eifert, G. H., Lejuez, C. W., & McNeil, D. W. (1999). The effects of offset control over 20% carbon-dioxide-enriched air on anxious responding. Journal of Abnormal Psychology, 108, 624–632.CrossRefPubMed
Zvolensky, M. J., Lejuez, C. W., & Eifert, G. H. (2001). Offset control during recurrent 20% carbon dioxide-enriched air induction: relation to individual difference variables. Emotion, 1, 148–165.CrossRefPubMed
Metagegevens
Titel
Relations Among Perceived Control Over Anxiety-Related Events, Worry, and Generalized Anxiety Disorder in a Sample of Adolescents
Auteurs
Jamie L. Frala
Ellen W. Leen-Feldner
Heidemarie Blumenthal
Carolina C. Barreto
Publicatiedatum
01-02-2010
Uitgeverij
Springer US
Gepubliceerd in
Research on Child and Adolescent Psychopathology / Uitgave 2/2010
Print ISSN: 2730-7166
Elektronisch ISSN: 2730-7174
DOI
https://doi.org/10.1007/s10802-009-9365-6

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