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Item 9 of the Patient Health Questionnaire-9 (PHQ-9) queries about thoughts of death and self-harm, but not suicidality. Although it is sometimes used to assess suicide risk, most positive responses are not associated with suicidality. The PHQ-8, which omits Item 9, is thus increasingly used in research. We assessed equivalency of total score correlations and the diagnostic accuracy to detect major depression of the PHQ-8 and PHQ-9.
We conducted an individual patient data meta-analysis. We fit bivariate random-effects models to assess diagnostic accuracy.
16 742 participants (2097 major depression cases) from 54 studies were included. The correlation between PHQ-8 and PHQ-9 scores was 0.996 (95% confidence interval 0.996 to 0.996). The standard cutoff score of 10 for the PHQ-9 maximized sensitivity + specificity for the PHQ-8 among studies that used a semi-structured diagnostic interview reference standard (N = 27). At cutoff 10, the PHQ-8 was less sensitive by 0.02 (−0.06 to 0.00) and more specific by 0.01 (0.00 to 0.01) among those studies (N = 27), with similar results for studies that used other types of interviews (N = 27). For all 54 primary studies combined, across all cutoffs, the PHQ-8 was less sensitive than the PHQ-9 by 0.00 to 0.05 (0.03 at cutoff 10), and specificity was within 0.01 for all cutoffs (0.00 to 0.01).
PHQ-8 and PHQ-9 total scores were similar. Sensitivity may be minimally reduced with the PHQ-8, but specificity is similar.
Pathological worry is a hallmark feature of generalised anxiety disorder (GAD), associated with dysfunctional emotional processing. The ventromedial prefrontal cortex (vmPFC) is involved in the regulation of such processes, but the link between vmPFC emotional responses and pathological v. adaptive worry has not yet been examined.
To study the association between worry and vmPFC activity evoked by the processing of learned safety and threat signals.
In total, 27 unmedicated patients with GAD and 56 healthy controls (HC) underwent a differential fear conditioning paradigm during functional magnetic resonance imaging.
Compared to HC, the GAD group demonstrated reduced vmPFC activation to safety signals and no safety–threat processing differentiation. This response was positively correlated with worry severity in GAD, whereas the same variables showed a negative and weak correlation in HC.
Poor vmPFC safety–threat differentiation might characterise GAD, and its distinctive association with GAD worries suggests a neural-based qualitative difference between healthy and pathological worries.
Different diagnostic interviews are used as reference standards for major depression classification in research. Semi-structured interviews involve clinical judgement, whereas fully structured interviews are completely scripted. The Mini International Neuropsychiatric Interview (MINI), a brief fully structured interview, is also sometimes used. It is not known whether interview method is associated with probability of major depression classification.
To evaluate the association between interview method and odds of major depression classification, controlling for depressive symptom scores and participant characteristics.
Data collected for an individual participant data meta-analysis of Patient Health Questionnaire-9 (PHQ-9) diagnostic accuracy were analysed and binomial generalised linear mixed models were fit.
A total of 17 158 participants (2287 with major depression) from 57 primary studies were analysed. Among fully structured interviews, odds of major depression were higher for the MINI compared with the Composite International Diagnostic Interview (CIDI) (odds ratio (OR) = 2.10; 95% CI = 1.15–3.87). Compared with semi-structured interviews, fully structured interviews (MINI excluded) were non-significantly more likely to classify participants with low-level depressive symptoms (PHQ-9 scores ≤6) as having major depression (OR = 3.13; 95% CI = 0.98–10.00), similarly likely for moderate-level symptoms (PHQ-9 scores 7–15) (OR = 0.96; 95% CI = 0.56–1.66) and significantly less likely for high-level symptoms (PHQ-9 scores ≥16) (OR = 0.50; 95% CI = 0.26–0.97).
The MINI may identify more people as depressed than the CIDI, and semi-structured and fully structured interviews may not be interchangeable methods, but these results should be replicated.
Declaration of interest
Drs Jetté and Patten declare that they received a grant, outside the submitted work, from the Hotchkiss Brain Institute, which was jointly funded by the Institute and Pfizer. Pfizer was the original sponsor of the development of the PHQ-9, which is now in the public domain. Dr Chan is a steering committee member or consultant of Astra Zeneca, Bayer, Lilly, MSD and Pfizer. She has received sponsorships and honorarium for giving lectures and providing consultancy and her affiliated institution has received research grants from these companies. Dr Hegerl declares that within the past 3 years, he was an advisory board member for Lundbeck, Servier and Otsuka Pharma; a consultant for Bayer Pharma; and a speaker for Medice Arzneimittel, Novartis, and Roche Pharma, all outside the submitted work. Dr Inagaki declares that he has received grants from Novartis Pharma, lecture fees from Pfizer, Mochida, Shionogi, Sumitomo Dainippon Pharma, Daiichi-Sankyo, Meiji Seika and Takeda, and royalties from Nippon Hyoron Sha, Nanzando, Seiwa Shoten, Igaku-shoin and Technomics, all outside of the submitted work. Dr Yamada reports personal fees from Meiji Seika Pharma Co., Ltd., MSD K.K., Asahi Kasei Pharma Corporation, Seishin Shobo, Seiwa Shoten Co., Ltd., Igaku-shoin Ltd., Chugai Igakusha and Sentan Igakusha, all outside the submitted work. All other authors declare no competing interests. No funder had any role in the design and conduct of the study; collection, management, analysis and interpretation of the data; preparation, review or approval of the manuscript; and decision to submit the manuscript for publication.
Microscopic and textural observations were made on ice samples cored from Blue Glacier slightly below the equilibrium line to depths of 60 m. Observations were started within a few minutes after collection. Water was found in veins along three-grain intersections, in lenses on grain boundaries and in irregular shapes. Gas was found in bubbles in the interior of crystals, in bubbles touching veins, and locally in veins. Vein sizes showed some spread; average cross-sectional area was about 7 × 10−4 mm2 with no discernible, trend with texture or depth except within 7 m of the surface. Before the samples were examined they could have experienced a complex relaxation which could have changed them significantly. As a result it is not possible to determine the in situ size of veins, but an upper limit can be determined. Also it is not possible to predict intergranular water flux per unit area, but 1 × 10−1 m a−1 represents an upper limit. In coarse-grained ice the water flux density is likely to be even smaller, because of a low density of veins, and blocking by bubbles. This indicates that only a very small fraction of the melt-water production on a typical summer day can penetrate into the glacier on an intergranular scale except possibly near the surface. The existence of conduit-like features in several cores suggests that much melt water can nevertheless penetrate the ice locally without large-scale lateral movements along the glacier surface. The observed profile of ice temperature indicates that the intergranular water flux may be much smaller than the upper limit determined from the core samples.
We used observations and modeling of Siple Dome, West Antarctica, a ridge ice divide, to infer the importance of linear deformation mechanisms in ice-sheet flow. We determined the crossover stress (a threshold value of the effective deviatoric stress below which linear flow mechanisms dominate over nonlinear flow mechanisms) by combining measurements of ice properties with in situ deformation rate measurements and a finite-element ice flow model that accounts for the effects of viscous anisotropy induced by preferred crystal-orientation fabric. We found that a crossover stress of 0.18 bar produces the best match between predicted and observed deformation rates. For Siple Dome, this means that including a linear term in the flow law is necessary, but generally the flow is still dominated by the nonlinear (Glen; n = 3) term. The pattern of flow near the divide at Siple Dome is also strongly affected by crystal fabric. Measurements of sonic velocity, which is a proxy for vertically oriented crystal fabric, suggest that a bed-parallel shear band exists several hundred meters above the bed within the Ice Age ice.
One of the questions still unanswered concerning the surge behavior of glaciers concerns their quasi-periodic occurrence. Some results on the phenomenological connection between local cumulative balance and surge initiation of Variegated Glacier, Alaska, U.S.A., are discussed here. Based on climate data from neighboring weather stations, an empirical relation between precipitation, temperature and local mass balance is established and used to reconstruct the annual balance at a location in the accumulation area back to 1905. Between the last four surges in 1946/47, 1964/65, 1982/83 and 1994/95, the ice-equivalent cumulative balance was 43.5 m on average, with a 1σ error of 1.2 m. Although the existence of a surge level cannot be directly interpreted in physical terms, it explains the variable length of the quiescent periods of Variegated Glacier by variations in the accumulation rate prior to the surge. We use the surge level to hindcast former unobserved surges, to compare the results with other surge datings obtained from photographs and to establish a complete surge history for Variegated Glacier for the 20th century.
As part of a project to investigate the flow of ice at low effective stress, two independent strain-gauge systems were used to measure vertical strain rate as a function of depth and time at Siple Dome, Antarctica. The measurements were made from January 1998 until January 2002 at the ice divide and a site 7km to the northeast on the flank. The strain-rate profiles place constraints on the rheology of ice at low stress, show the expected differences between divide and flank flow (with some structure due to firn compaction and probably ice stratigraphy), and suggest that the flow of the ice sheet has not changed much in the last 8.6 kyr. The strain rates show an unexpected time dependence on scales ranging from several months to hours, including discrete summer events at the divide. Time dependence in strain rate, water pressure, seismicity, velocity and possibly basal motion has been seen previously on the Siple Coast ice streams, but it is especially surprising on Siple Dome because the bed is cold.
As part of a larger program to measure and model vertical strain around Siple Dome on the West Antarctic ice sheet, we developed a new sensor to accurately and stably record displacements. The sensors consist of optical fibers, encased in thin-wall stainless-steel tubes, frozen into holes drilled with hot water, and stretched from the surface to various depths (up to 985 m) in the ice sheet. An optical system, connected annually to the fibers, reads out their absolute lengths with a precision of about 2 mm. Two sets of five sensors were installed in the 1997/98 field season: one set is near the Siple Dome core hole (an ice divide), and a second set is on the flank 7 km to the north (the ice thickness at both sites is approximately 1000 m). The optical-fiber length observations taken in four field seasons spanning a 3 year interval reveal vertical strain rates ranging from −229 ± 4 ppm a−1 to −7 ± 9 ppm a−1. In addition to confirming a non-linear constitutive relationship for deep ice, our analysis of the strain rates indicates the ice sheet is thinning at the flank and is in steady state at the divide.
Measurement of geometry, motion, and mass balance from Variegated Glacier, Alaska portray conditions in this surge-type glacier close to the mid-point of its 20 year surge cycle. Comparison of longitudinal profiles of ice depth, surface slope, and surface speed indicate that the motion occurs largely by internal deformation assuming the ice deforms according to the experimental law of Glen. Surface speed is not noticeably affected by local surface slope on the scale of the ice thickness or smaller, but correlates well with slope determined on a longitudinal averaging scale about one order of magnitude larger than the ice depth. The rate of motion on Variegated Glacier agrees well with rates on non-surge type temperate glaciers which have similar depth and slope. Although the (low regime at the time of the measurements is apparently typical of temperate glaciers, a large discrepancy between the balance flux needed for steady state and the actual flux is indicative of a rapidly changing surface elevation profile and internal stress distribution.
Variegated Glacier is a surge-type glacier in the St Elias mountain range in Alaska. The interval between surges is about 20 years; the last one occurred in 1964 to 1965. This glacier has been studied extensively since 1973 (Bindschadler and others, 1977). Thus far, measurements of ice velocities have been restricted to the surface. They have been analyzed using geophysically measured ice depths, in order to estimate ice velocities in the ice mass and at the base (Bindschadler and others, 1978). From 1973 to 1977 the distribution of annual ice velocities along most of the length of the glacier can be explained primarily by internal deformation without major contribution from sliding at the base. However, the variation of surface velocity with time gives definite indication that sliding occurs in summer and that the average summer rate is increasing progressively from summer to summer and that in a zone 5 to 7 km below the head of the glacier the summer-to-summer increase in inferred sliding rate is especially rapid. This is a notably distinguishing feature, which is probably indicative of a build-up toward the next surge. In order to obtain direct information about sliding-rates and water pressures at the base in this zone, a bore hole was drilled to the bottom of the glacier about 6 km below the glacier head. Observations in the hole started in June 1978 and were continued until 31 July 1978. The hole connected to an englacial water system at a depth of 204 m whereupon the water level dropped gradually to about 100 m below the surface. The last 6 m above-the base at 356 m could be drilled only by means of a cable tool because of the presence of debris-rich ice. Upon reaching the bottom, the water level increased rapidly to the firn water table at about 8 m below surface. Large variations in water level of about 200 m occurred during the following period of observation of 35 d. Major events such as audible icequakes, heavy rainfalls, and a period of unusually high ablation were associated with abrupt increases of water level up to the firn water table. High water pressure at the bottom drove a flow of muddy and sandy water upward in the hole. Consequently high freezing rates in the lower 150 m of the hole produced a very rough bore-hole wall covered with ledges, coral-reef-like features, grooves, and pockets filled with sand. Near the bottom, embedded rocks stuck out of the bore-hole wall. These features were recognized by bore-hole television. The bore-hole bottom consisted of sand which continuously proliferated and washed into the hole. Attempts to remove this sand by means of a sand pump failed, the bailed-out sand being replaced immediately. From bore-hole inclinometry an internal deformation of the ice mass of 0.22 m d−1 was obtained. Together with average surface velocity of 0.47 m d−1 we get a sliding velocity of 0.25 m d−1, averaged over the time of observation. This result confirms the sliding velocities inferred from surface velocity measurements. It also lies on the exponential trend line of increasing summer-to-summer velocities showing a doubling of sliding velocities about every two years (Bindschadler and others, unpublished). This strongly indicates that the next surge is likely to occur in the early eighties. Input of water from the surface probably will play a role in triggering the surge.
A reconnaissance program has been carried out to identify problems caused by glaciers in a large proposed hydroelectric development in the Susitna River basin of Alaska. Balance measurements on the major glaciers have been initiated, and long-term balance between 1949 and 1980 has been estimated from existing photo sets. From the latter it appears that shrinking of the glac!iers, which comprise 4% of the basin area, may have contributed appreciably to the measured basin runoff. A potential instability in the drainage of Eureka Glacier, on the edge of the basin, has been identified. The glaciers of the basin seem to be largely temperate, and most of them are surging or pulsing types. Velocity measurements show seasonal variations that suggest appreciable contribution to the motion from basal sliding. A study of the moraines of Susitna Glacier, which is a surging type, indicates that no surge is imminent. Glacier-dammed lakes exist in the basin; they are small but could be enlarged by surging or other mechanisms. Some general problems in the estimation of the transport of suspended sediment are noted.
A relatively lightweight and simple airborne system for surface elevation profiling of glaciers in narrow mountain valleys has been developed and tested. The aircraft position is determined by kinematic global positioning system (GPS) methods. The distance to the glacier surface is determined with a laser ranger. The accuracy is about 0.3 m, sufficient to permit future changes to be observed over short time intervals. Long-term changes can be estimated by comparison of profiles with existing maps. Elevation profiles obtained in 1993–94 from three glaciers in central and south-central Alaska are compared with maps made about 1950. The resulting area-averaged, seasonally corrected thickness changes during the interval are: Gulkana Glacier (central Alaska Range)–11 m, Worthington Glacier (central Chugach Mountains) +7 m, and Bear Lake Glacier (Kenai Mountains) −12 m. All three glaciers retreated during the interval of comparison. The estimated uncertainty in the average thickness change is ±5 m. which is mainly due to errors in the existing maps. Constraints on the accuracy of the maps are obtained by profiling in proglacial areas.
Ice temperature was measured in and around the chaotically crevassed south margin of Ice Stream B, Antarctica, from 1992 to 1994. The temperatures at 30 m depth in the chaotic zone are about 12 K lower than in the adjacent uncrevassed ice, due to the ponding of cold winter air. At depths greater than 150 m, there is clear evidence of internal heating of the ice due to the large shear déformation rate in the marginal zone. Analysis of the depth of cooling below the crevasses and of the internal heating gives two pieces of information. First, over the last half century the lateral shear stress averaged 2.0 x 105 Pa in the top third of the margin and, second, the margin moved outward at an average rate of 7.3 m a−1. These values do not involve any assumptions about the How law of ice. The uncertainties are roughly 20%. The value of lateral shear stress indicates that the most of the drag on the ice stream is along its sides.
A surge of West Fork Glacier, a temperate glacier in the Susitna Basin of the Alaska Range, began soon after the end of the 1987 melt season and terminated on 6 July 1988. Reconnaissance measurements of balance, elevation and speed had been made from 1981 to 1983. Daily measurements of surface speed at two points 9 km apart and of the characteristics of the stream draining the glacier were begun during the surge and continued through the following year. The maximum displacement of the ice during the surge was about 4 km; the maximum change in surface elevation was about 120 m. Between the time of the start of detailed observations on 12 February 1988 and the onset of a complex termination phase during the last month of the surge, the speed was almost constant, and the water discharge was totally free of turbidity, indicating that no basal water was escaping from the glacier. During the termination phase, sharp changes in speed occurred, almost simultaneously at the two observation sites; each deceleration event was accompanied by high sediment concentration and high water discharge. This behavior is similar to that observed on Variegated Glacier during its 1982-83 surge. The mechanism of triggering (related to surface water input and the disruption of the internal drainage system) and the cause of the fast motion were probably the same for both surges, even though there are substantial differences in size and mass-balance characteristics.
During the decade prior to its 1982–83 surge, Variegated Glacier experienced progressive changes in geometry and velocity. It thickened in the upper 60% and thinned in the lower 40% of its 20 km length. Thickness changes were up to 20%. Annual velocity increased by up to 500%, reaching a maximum of 0.7 m d−1 in the year before surge onset. Amplitude of seasonal variation in velocity increased up to 0.3 m d−1 by 1978, but did not increase markedly after that. The changes in velocity were larger than predicted from changes in deformation rate caused by changes in shear stress and depth. This anomalous velocity was especially large after 1978 in the zone of thickening on the upper glacier. If it is assumed to arise from basal sliding, the inferred pattern of sliding shows qualitative features consistent with a direct effect from basal shear stress and an inverse effect from effective normal stress. A drop in effective normal stress in a zone of decreasing surface slope up-glacier from the largest thickness increase may have been significant in the initiation of surge motion in 1982.
A transverse profile of velocity was measured across Ice Stream B, West Antarctica, in order to determine the role of the margins in the force balance of an active ice stream. The profile extended from near the ice-stream center line, through a marginal shear zone and on to the slow-moving ice sheet. The velocity profile exhibits a high degree of shear deformation within a marginal zone, where intense, chaotic crevassing occurs. Detailed analysis of the profile, using analytical and numerical models of ice flow, leads to the following conclusions regarding the roles of the bed and the margins in ice-stream dynamics:
(i)The overall resistive drag on the ice stream is partitioned nearly equally between the margins and the bed and, thus, both are important in the force balance of the ice stream.
(ii)The ice within the chaotic zone must be about 10 times softer than the ice in the central part of the ice stream.
(iii)The average basal shear stress is 0.06 × 105 Pa. This implies that the entire bed cannot be blanketed by the weak, deformable till observed by Engelhardt and others (1990) near the center of the ice stream — there must be regions of increased basal drag.
(iv)High strain rates and shear stresses in the marginal zones indicate that strain heating in the margins may be significant.
While the exact quantitative values leading to these conclusions are somewhat model and location-dependent, the overall conclusions are robust. As such, they are likely to have importance for ice-stream dynamics in general.
Accumulation studies along the lowermost 100 km of Jakobshavns Isbræ show that the local net balance above the equilibrium line (1210 m elevation in 1986) is significantly less than that measured along the EGIG line about 100 km further north. This indicates the presence of a precipitation low in this region which will affect any global mass-balance assessment for the Jakobshavns Isbræ drainage basin. Comparison of the estimated calving and ablation fluxes shows that calving removes about twice as much mass from this drainage basin as does melting. Basal melting over the entire basin accounts for about 20% of the total ice loss by ablation. Temperature measurements at 12 m depth along the same section of the Isbræ show the warming effects of refreezing meltwater and cooling effects of severe crevassing. In addition, there is a significant variation in temperature across the fast-moving ice stream which is probably caused by deformation heating in the shear margins which delineate the ice stream within the ice sheet. This lateral temperature gradient could be important in ice-stream dynamics through its effects on ice rheology. Detailed measurements within the percolation fades show that surface melt can penetrate up to 3 m by piping in cold firn, and, upon refreezing, can cause significant warming at these depths.
This paper presents results obtained with the Jodrell Bank - IAC two-element 33 GHz interferometer, located at the Teide Observatory on Tenerife, which is designed to measure the level of the Cosmic Microwave Background (CMB) fluctuations on angular scales of 1° and 2°. The result from a maximum likelihood analysis of observations taken at Dec +41° of δTl = 63+7-6μK at l = 208 ± 18 is comparable with those of Boomerang and Maxima. The contribution of possible foreground contaminants are considered.
To allow an objective study of transition region blinkers an automated identification program has been developed to analyse the CDS/SoHO data. The general properties of blinkers identified by this method confirmed the properties of those identified by eye in previous studies. Blinkers have typical lifetimes of about 20 minutes, areas of about 2.8 × 107 km2 and intensity enhancement factors of about 2. For the first time, blinkers have been identified in active regions. These blinkers have the same general properties as quiet-region blinkers. The automated approach found many more blinkers than previously had been found giving a global birth rates of about 9 s−1 for quiet-region blinkers and 16 s−1 for active-region blinkers. Most blinkers, active or quiet region, are red shifted with typical velocities of about 13 km s−1. Finally, we can confirm that blinkers are not enhancements in temperature, but either enhancements in density or increases in the filling factor.